HRM statistics that we don't have yet (and a summary of previous conversation about them)

Hi I originally made a HRV app for the Bangle 1, which I can probably check and change if it's busted since I last updated it. I can definitely make it more efficient. I've been looking at making a similar one for the Bangle 2, which I recently got; it's a great watch but the PPG signal is definitely harder to work with either raw or filtered, signal moves around a lot probably because of the auto-adjustments it seems to make. Will try get something working for it though, I'm trying different options around polling rates and locking the LED auto-adjustment to see if I can get it more stable.

For Sp02, I doubt this would give anything useful - SP02 is usually red + IR light you need to measure not green because your blood absorbs green. I've seen notes on research using different shades of green but not green + IR. You basically do comparisons of the 2 signals to see light absorption at different wavelengths in the same kind of range but because green and IR are so far apart I'm not sure it would work. Datasheet doesn't suggest it has a red LED. It's possible they have a different similar model that uses a red LED instead of the green tailored more for Sp02.

For blood pressure, it looks like you need quite a clean, stationary signal for this. I actually think it's possible to get blood pressure from recorded data out of Bangle 1 easily. The caveat is the algorithm would probably have to be done outside of the watch so would need to use a phone or something that can handle more power and transfer the data by bluetooth or do it retrospectively. The easiest methods I've seen take PPG signals directly and run them through a neural net. The Bangle can run tensorflow so theoretically, if you get a small enough tflite model that can take a low 25Hz signal it could work but I think the pre-filtering you need to do beforehand as well with it might all be too much.