I am working on getting this compiled, some QT6 errors right now on my Librem5-Purism crimson but it is working on my Ubuntu’ish laptop. I used my old Polar H1 with my N900, I find it is the best way to set my workout cruise control especially choosing gears when cycling. The Polar H10 uses BTle and is powered by a cr2025 cell which is better than the lithium cell which lasted over 10 years in the H1 before becoming unusable.
It is nice, more than just a rate number, and looks like it will work well on the phone UI. I can record as well as keep an eye on my own ECG trace(You can get a lot of cardiology information from analysis of the trace even if it is just two pads) which is way more high tech than my old H1. I suppose if I wear the HRM band over my right shoulder and under my left armpit to approximate ECG lead II((white–>red wires) axial electrical propagation path lets you best visualize the P wave) vs the less useful lead I(white–> black wires) across the chest which is the normal band wear. If you want to geek out on electrocardiology like I do start with this:
https://geekymedics.com/how-to-read-an-ecg/
