I made my own heart rate app (using gemini at first and then Claude for lots of further edits). https://xosh.org/heart-rate/ https://github.com/SMUsamaShah/heart-rate it's all offline. UI needs more work but me and my wife are the only users therefore it doesn't matter that much.

At one point I added the same EVM based heart rate detection but that requires sitting very still. I use it on my phone mainly therefore the common finger method is easiest one to use.