They don’t. This is not really a simple ask as getting good data isn’t simple.
-have to use ble over ant+ (so need some way to tell users which option they should pick which is more a UX problem)
-have to identify which strap is being used to record with. Mix of a UX problem in telling users which brands they should buy and a data issue to handle the data from different sources differently
-positioning the strap is not so easy. Need so way to inform users that while they get good hr data their hrv needs better positioning
- with recorded data need to flag if it has bad data in it so should be ignored
That’s all before doing the actual calculations are done