Interesting ideas! I'm don't do mobile dev either, but regarding your first point, I think the idea is very cool, but taking that direction would be very difficult. Achieving what you suggest the easy way is through a mobile app. The problem is that the if we're looking at older phones that are not supported anymore, they aren't secure, so we could run into problems there. The second option you suggested, which is a single purpose ROM seems very cool, but it also seems very daunting, as it is hardware specific from my understanding.

I'm not familiar with the animal prosthetic field too much, but could be an idea.

thank you, and please share more ideas if you can :)