We're developing simultaneously on iOS and Android. The Android version of the app is built on a cross-development framework that we should be able to extend to other platforms shortly after launch. There is also a web client in the works that will be compatible with all platforms.
The coverage area of one Point will depend on the layout and air circulation of your home. As a rule of thumb, one Point should cover approximately 500 sqft, 45 sqm), before the air quality measurements will begin to degrade. Sounds travel further, and if you can hear sounds, then so can Point.
Only processed sound events and raw data of air quality, temperature and humidity is sent to our servers. No raw sound data leaves the device. Beta backers will be able to retrieve all aforementioned uploaded data through an API. We are planning on opening the API for everyone in the future.
No. Many of you have asked about carbon monoxide and it is definitely on our radar. There is a trend-shift in technology happening. Current sensors are electro-chemical and have limited lifetime. Newer ones that are in the pipeline (maybe 18 months) are smaller, easier to integrate and have vastly longer lifetime. We didn't want to put a sensor in Point that would feel old less than a year after shipping.
We're using a completely new Wifi-chipset (from the world's leading wifi-chipset manufacturer) that has yet to be certified by Apple. We can't guarantee that it will be, but we would be very surprised if it's not and will start working on HomeKit as soon as that happens.