@marcrie
If consuming from app rather than from watch and interested in all day measurements and not just when tracking an activity, then best option is Garmin as its the only one that uses a 2min avg on its HR graphing , most others are using a 5 or 10 min periodic or avg reading.
Note that if checking the HR from the watch face its unlikely to be continuous as to save battery (whether amoled or mip) the HR data point on the watch face will only update periodically i.e. on Garmin its either a 5s or 1min interval - depends on the watch face build. Not sure of other brands but suspect its similar. To see active HR when not tracking activity you would have to open HR widget which does show active live HR.
For continous HR 24/7 and not just during tracking (during tracking all watches offer continuous 1s reads):
All garmins offer this as standard (its the only option).
Wear os Pixel / Pixel 2 (note locked to android).
All Fitbits offer this.
Samsung GW series (wear os so locked to android)
Not sure:
coros, polar and suunto - I know that some suunto do but not all. Rest of wear os (fossil gen 6, ticwatch pro 5, xiaomi watch 2 pro).
Doesn’t:
Withings (10 min); amazfit (1 or 10 min), huawei (periodic or real time contiuous which is dynamic like apple watch in that continuous when being active but if sitting still i.e. inactive it becomes periodic).
Wouldn’t suggest going outside these brands if want a level of accuracy.
