The magnets have no affect on cell phones, tablets and modern laptops with flash storage. I would not recommend putting them in direct contact with any spinning harddrive. Having said that, I have kept two pens in my laptop bag for a few months, with an external spinning hard drive, and have had no ill effects.
The pens do not have an effect on modern day plastic credit cards, such as VISA and Mastercard. Yet, it is not recommended to put the pens in contact with disposable cardboard magnetic strip cards, such as the ones used in London's transit system.