PPG analysis beyond HR at rest

@Mi I'm really heartened to see your Confidence>90 graph. I know right now we struggle with movement but it's a big help having something that knows when it's accurate :)

What we need ideally is the raw hrm signal, the accelerometer, and the values from your other hrm

Yes - and ideally use an ECG one for the second HRM. I have something that straps on my chest which I think would give much more sensible figures during exercise.

A test harness along the lines of https://github.com/gfwilliams/step-count would be perfect - and then we can build up some data and make some properly educated tweaks to the algorithm