Share this project


Share this project

Challenger fits on any racket and instantly gives you feedback about your swing.
Challenger fits on any racket and instantly gives you feedback about your swing.
685 backers pledged $102,934 to help bring this project to life.

Use this space to cheer the creator along, and talk to your fellow backers.

Have a question?

Only backers can post comments. Log In
    1. Missing avatar

      Tim Eacott on

      So sad that this one did not work out, but at least these guys failed with some grace and humility.
      I am a backer of two other Kickstarter projects that have failed to deliver and those other guys were complete dickwads!

    2. Enrico C

      I lose faith in KS now.

    3. Scott on

      Outcomes like this one is why, after backing over 200 items, I VERY rarely consider backing any others.

    4. Missing avatar

      Alvin Vuu on

      It's been awhile since I have been on KS. This one makes me sad :( The product sounded amazing. Sad to see it fail.

    5. Lavie Sak Creator on

      @Peter - Thank you for your offer to help. I just want to reiterate I would love to share our work with everyone, but the moment I do, the option around partnerships and any sort of revival are essentially made impossible. That being said, if there are folks with the needed skills sets we can definitely further discuss. Can you send me a message at and we can further discuss?

      I apologize if it looks like we gave up. We put everything we had into it. As for the updates, again sorry, I really tried to be transparent and share them in a timely manner. With this latest update, I was really hoping to offer good news that the newest prototypes were up and running, but unfortunately that wasn't the case. We sent some videos the Challenger being used on court with USC and some testing videos. The past iterations worked, but this latest one has a critical bug.

      Again thanks for support and I look forward to your message.

    6. Peter R. Gomez on

      I am a mechanical engineer and I would be willing to do whatever I could to help. I realize Sergey has left, and while I may not have the experience he does I'm sure I could find contacts that would be able to help with anything too far out of my grasp.

      Lavie, what is the next step? I believe Challenger can get completed, if you open it up to the backers here and let us try and help you. You don't need to pay us, we're all here because we want this product to come to fruition. For Challenger to finish, we need to know everything that happened, and what the state of the project is at the moment.

      You mention an Engineering Package, but you don't want to give that to us without exploring other possible avenues for funding. What are these avenues? Have you tried Shark Tank/Dragon's Den? Look, I understand you are in debt and it's been tough. But I just feel that these updates you've been sending out have been too infrequent, and also too vague. Yeah, the photos are nice; but that doesn't tell us anything about how the product functions.

      Anyways, I am disappointed like many others here. But the disappointment stems from the fact that you seem to have given up rather than the state of the project. If you have, I understand. But you should release that Engineering Package soon then, so that others here can finish what you started.

      What can we do to help you?

    7. Missing avatar

      J on

      So, backers, who has the skills here to try and help?

    8. Lavie Sak Creator on

      @J - Electrical to troubleshoot the current PCB and mechanical to work on DFM and ensure the production progress is inline. The software/algorithms are not perfect, but for now are set. The mobile app is fully designed but not developed ($45K should handle that). More details on the estimate here:…


    9. Missing avatar

      J on

      These are big numbers.

      When thou say electrical and mechanical, you're talking about pcb design and sensors?

      So software is all done?

    10. Lavie Sak Creator on

      @Philip - the key is finding another person with Sergey's skill set and the funds to pay for troubleshooting and production.

    11. Lavie Sak Creator on

      @J - The skills that are needed would be on the electrical and a bit on mechanical side, at least for this version. The bugs in the current version need to be fixed. Once they are, we continue DFM (design for manufacturing) and enter production. As Sergey left, we need people with those skill sets and the money to pay them. Rough cost to complete the required number of units (~700) would be $125K assuming we don't change any of the firmware/algorithms. A MVP (minimum viable product) app can be made for another $45K.

    12. Philip Maidens

      What would it take to resurrect the product? Its such a great idea.

    13. Missing avatar

      J on

      I've backed some projects on here that have not worked out, awful communication, no response to backers questions and nothing like this in terms of expenditure.

      Backers have asked, and Lavie's provided the numbers pretty quickly, that to me us a rarity on Kickstarter and deserves respect.

      I would be interested to know how much extra money might be needed to bring this to fruition and also what skills are needed.

    14. Lavie Sak Creator on

      re: Expenditures - More transparency into how the funds were spent. The cost of contractors and prototyping exceeded the amount of funds we received through Kickstarter. Core expenditures directly for development.

      Firmware/Algorithm Work - Russia
      10/28/14 - $3,375
      11/17/14 - $13,650
      12/10/14 - $13,450
      6/12/15 - $22,400
      7/6/15 - $16,800

      Algorithms consultant
      9/22/14 - $1,252.67

      Mobile App Dev/Design
      12/4/14 - $2,520
      11/26/14 - $3,765
      7/10/15 - $3,375

      Beta prototype costs (materials and services for 20 units)
      Last Nov until now - $7,980.73

      Last 2 iterations of prototypes (materials and services)
      ~$6,000 each: $12,000

      Total of core expenditures without cost of equipment, workspace, and travel: $100,568.40

      Those costs for development exceeds the amount of money received from backers (minus the Kickstarter fees) of $90,714.12 by $9,854.28.

      As mentioned in the update, the cost of development was much higher than expected. This left us without enough funds to enter production. We would have loved to stay local but we required specific skill sets which are in very high demand and costly. A year’s salary for 1 data scientist/physicist would have exceeded our Kickstarter funding.

      re: "If he ever comes good with Shot stats that he might one day remember us." - 100%

    15. Missing avatar

      J on

      Firstly, as a backer like everyone else, I'm disappointed that Shot Stats looks like it's not going to come to fruition.

      Lesson I have learnt from this and other kickstarter projects is that if the financial target is low then the creator probably hasn't really thought through the scale of potential costs and built in enough contingency for bumps along the way.

      The other lesson is around the project plan, the timescales, they're always overly optimistic.

      With regards to this project, my gut feel is that communication has been good, responses have been quick, it just feels that it was a bigger task than anticipated and Lavie was desperate to try and make it work but once on the slippery slope it is hard to reverse it.

      The money pledged has been spent trying to bring this to fruition, there is no money for refunds.

      Sure I've lost some money but it's not enough to want to hassle the creator who appears to have done his best efforts.

      He can share some accounts with us, I'm not that bothered, I trust him, and even if it turns out he spent it unwisely, what are we going to do exactly?

      All we can do is be more careful in future projects, wish lave well, and hope that if he ever comes good with Shot stats that he might one day remember us.

      C'est la vie.

    16. Wai Man Young on

      My first lemon Kickstarter, also one of the costliest. I had such high hopes in a good ending.
      I'll be even more careful with funding next time.

    17. Missing avatar

      Joseph Clancy on

      Hi Lavie,
      I know what you have stated, but I'm requesting that you refund my pledge. Project Creators are required to fulfill all rewards of their successful fundraising campaigns or refund any Backer whose reward they do not or cannot fulfill.
      Terms of use are here:

    18. Missing avatar

      Jordan on

      Agreed with Jason. Expenditures Detail need to be posted ASAP.

    19. Missing avatar

      Alvin Vuu on

      very sad, with the money I couldve purchased something

    20. Missing avatar

      Peymaan Sagafi on

      Very disappointed! wasted $250 and asked friends to pledge too. learned my lesson not to back a project without a prototype. I agree with Jason, Lavin needs to share how the money was spend in addition providing the code, designs and all parts to be sent to the backers. Mike

    21. Jason Alexander on

      Very sad. Any chance you could post a public statement of your G/L? I'd love to understand HOW you spent the funds.

    22. on

      Rather than throwing in the towel, why not start another fundraising round, like most startups? Or release a pared down version..? Ship SOMETHING. At this point, I'll settle for two cases of Pro Penn marathon balls.

    23. Colyn Bunn on

      I'm really really not happy either as wasn't a small amount of money either , i think with all the other products out there they have decided to give up and don't think they have gone about it the right way in telling us. and as for offering us a free hit if we are local is an insult.

    24. Missing avatar

      kfstudio on

      So there is no product and the backer just announced he is not giving refunds. Disgraceful. Kickstarter should get involved, or the Better Business Bureau.

    25. Missing avatar

      sandro.vettori on

      PLEASE !!

    26. Missing avatar

      J on

      Appreciate your efforts, would just say, as I have before, it's really important that your timescales are realistic.

    27. Lavie Sak Creator on

      @J - 100% agree coaches are important and will always have their place. As for the timeline - we are currently modifying a conventional oven to create a make shift reflow oven for our PCBs. Can't afford an actual one. That is almost complete. When done, we will be hand assembly the 20-25 prototypes, upload the latest firmware, and send out an announcement.

    28. Missing avatar

      J on

      Lavie, I understand and agree, but as I said, it won't tell you about your technique.

      It won't tell you that you need to adjust your grip. Won't tell you that your stance is too closed etc.

      What it will do is give you a relative indication regarding power, spin and control but not technique.

      Anyone who is thinking of getting this to replace a coach is a little off course.

      Any updates on timescales?

    29. Lavie Sak Creator on

      @J - The plan was (with enough funds) to create a knowledge base from collected quantitative feedback that could help supply qualitative feedback (drills, technical recommendations, even videos). Obviously, version 1 wouldn't have this, but the hope is to bring this to future versions. The sky's the limit, pending funding.

      As a coach myself, I know nothing can replace a coach - but I know that a lot of us could use the help. From our site - "No hardware will ever replace the experience and intuition of a human coach. We developed Challenger not to replace a teacher, but to enhance the teaching experience. We want to provide more data for analysis — with or without a coach — to illuminate technique in a way that hasn’t been accessible to most players - until now. We love tennis; it's really given us so much. We hope that Challenger and products like it can not only help us grow as players, but also help the game of tennis grow so that it can be cherished by future generations. We want this technology to help coaches teach rather than teach them how to coach."

    30. Missing avatar

      J on

      I'm stuck at the intermediate level and wish to improve but am too poor to afford a fulltime private coach to provide feedback on my technique. That's why shot stats seems very interesting to me.
      Shot stats will tell you very little about your technique, just the outcome.

    31. Lavie Sak Creator on

      @Anand - Thanks for offering to help and trust me I would LOVE to help improve your game with Challenger.

      Can you please email me directly at and we can further discuss about funding?


    32. Anand Bhatia on

      Lavie, I was one of the backers interested in the BETA.

      Let me know if you need me to campaign for additional funding and I can ask around in my Tennis Center here in North California.

      I'm stuck at the intermediate level and wish to improve but am too poor to afford a fulltime private coach to provide feedback on my technique. That's why shot stats seems very interesting to me.

    33. Missing avatar

      J on

      Thanks for prompt response, can't tell you how much I appreciate that and how big a plus point that is for you.

      Also appreciate the fact that you are putting your own money in.

      I mentioned to Lavie a while back the possibility of backers backing a bit more to bring this to fruition.

    34. Lavie Sak Creator on

      @Philip - We have a few leads who are awaiting a demo of this beta. We really believe in instant data (screen/speaker) along with the coaching know-how (app) to make the best use of that data.

      Thanks for support!

    35. Philip Maidens

      Hi Lavie
      It sounds like you need additional funding in order to complete the initial kickstarter orders. How is that coming along? Any interest in the market? There have been a number of new products on the market since your kickstarter launch (I am thinking Sony & Babolat etc) trying to do a similar thing to you, but I still think your idea of a dampener is far better than some sensor stuck on the end of a racquet with all the complications of accuracy from different racquets. Still keeping my fingers crossed..
      Best wishes

    36. Lavie Sak Creator on

      Hi J, Sergey here.

      Right now we've received most of the long lead-time components. We have all of the PCBs, tooling to assemble them, and certain 3D printed internal parts. We are still waiting on 50 sets of prototype housings to be shipped from China. They should have been completed on Friday, the 16th, and we are awaiting an update. We expect to have those here at the end of this week or the beginning of next week.

      We are also waiting on a mold for the rubber dampers on Challenger, which will be completed in 1-2 weeks and will allow us to make our own dampers in-house. The last holdout(s) are the electronic components. These are being ordered from a distributor in the US and so won't take more than 2-3 days to arrive, and with luck that order is going out tonight.

      Once we receive all the parts we should be able to assemble 20-25 prototypes within 1-2 weeks. The plan was originally to make 50 - and we will have enough parts for 50 with the exception of the electronic components. At the moment we can't afford to order electronic parts for all 50 sets, so we're settling on 20-25. About $4k of this batch is coming out of my personal finances at this point so we are hitting some hard limits. Of course if we do secure funding we can always order the rest of the parts to fill out the entire batch of 50 prototypes.

      That's about the long and short of it as of now. I'll post an update once the parts are in and I'm ready to start assembling them!

    37. Missing avatar

      J on

      Lavie, you need to be updating better than this, you keep giving dates, then keep missing them.

    38. Missing avatar

      Tim Eacott on

      Happy New Year 2016 to Lavie, Sergey and anyone else working on Shot Stats Challenger.
      Here's hoping that 2016 has a flying start with Beta testing, resolving the funding challenges and starting production!

    39. Lavie Sak Creator on

      @J - Long story short, most of the components have arrived but there have been delays on a few items, the housings and OLEDs in particular. There have been a few issues with the suppliers. Once all the pieces are here we will begin assembly and get some of them out to our testers (some of which are also backers). Our hope is that everything arrives by the beginning of the new year. We are trying our best to level set expectations but we keep hitting unseen delays. We will do our best to avoid them going forward.

      Thanks and Happy Holidays.

    40. Missing avatar

      J on

      End of December is here, how is progress?

    41. Lavie Sak Creator on

      @Anthony - We will be getting the latest prototypes by end of December and using them to offer trials to backers and pitch new investors.


    42. Missing avatar

      J on

      Not sure why people are asking for refunds, kickstarter doesn't work that way, it;s the risk you take.

      I've said it before, i trust in Lavie, just have to accept that this journey is going to be longer than planned and might need a little more help along the way.

    43. Lavie Sak Creator on

      @David - [Copy and paste from our response to Enrico] Unfortunately, we cannot issue you a refund at the moment as we do not have the funds to do so. Every penny of the Kickstarter campaign went directly back into prototyping, development, and pre-production efforts. Sergey and I have not taken any salary from those funds. In fact, all of our savings have gone into the company and our living expenses. That being said, when we are funded you will receive a refund.

    44. Missing avatar

      David Naylor on

      I'd be interested in a refund as well. Thanks.

    45. Lavie Sak Creator on

      @James - Please email with your change. We plan on shipping the shirts when we ship the units. Thanks!

    46. Lavie Sak Creator on

      @Enrico - Unfortunately, we cannot issue you a refund at the moment as we do not have the funds to do so. Every penny of the Kickstarter campaign went directly back into prototyping, development, and pre-production efforts. Sergey and I have not taken any salary from those funds. In fact, all of our savings have gone into the company and our living expenses. That being said, when we are funded you will receive a refund.

    47. Missing avatar

      James Larson on

      Was curious if I could change the size of the shirt I ordered with the $25 backing. Also, when do you think shirts might send out?

    48. Enrico C

      Sorry to say but I would like a refund.

    49. Lavie Sak Creator on

      Menno/Pallavi -

      Very sorry for the delay here. We've been heads down focusing on development and fundraising. We are planning an update in the next few days.


Show older comments