As a counterpoint to everything here, the Apple Watch just saved a friends life by telling them they were in AFib. Yes, it could be bad. Or it could be medically beneficial to people who are anxious and depressed and simply don’t have anyone to help them recognize it because they’re alone. Particularly during the pandemic, that would have been useful.
As long as no health data leaves my Apple Watch + iPhone, I am OK with local deep learning (or other models) running on my devices.
I do wish there were International standards and local laws supporting: all data staying on users' devices unless explicitly shared with health care providers, and also agreed upon standards for anonymizing explicitly shared data for the public good (research, AI training data, etc.)