Do you have a particular hardware sensor requirement needed to clone the body battery function? I’m interested in developing this too but always resisted getting a smartwatch due to privacy concerns. If there’s something available that’s Gadgetbridge compatible I’d be very interested.
Good news; I'm gifting you with the fruits of AI, that has collated 200+ papers on the topic. I know, I know; this is generous.
https://github.com/catigula/recovery