I had an exercise bike that came with a heart-rate band monitor, but it only pairs with the stationary bike. I wanted to use it for running to show heart rate zones. So I wrote an android app that pairs with the band, gets reading and make some nicer display. I had no idea how to write flutter, or talk to bluetooth devices, but github and chatGPT helped a lot.

https://github.com/kernyan/HeartRateBandHacking