You wanting more data does not give you license to assume consent for using a device you do not own to spy on a user. Even if a majority would have consented, assuming consent means that you are now co-opting some number of devices which do not belong to you to do things the owners of those devices do not want to happen.
Well - the user is using the device with a part that I created. If the user doesn't want to participate in enhancing the product, we need to go the old school way of enhancing products: Research. We need to conduct studies, do testing with test persons, etc.
This can be done, sure. But then your off-the-shelf app won't be available for 99 cents or for free, but cost more like 19.99 USD.
Might help streamlining the market, so I‘m open for that.
It’s extremely unethical, and should be illegal.