Does anyone know, in general, if a watch device already has a pulse measurement ...

pps43 · on July 16, 2020

You need two LEDs (one visible, one IR) to measure oxygen level, but only one for pulse.

wlesieutre · on July 16, 2020

Apple has apparently had both since their first watch models, but only uses them for heart rate. https://www.theverge.com/2014/9/9/6126991/apple-watch-four-b...

EDIT: Apple says it uses green LEDs during workouts and IR for background measurements. Maybe it’s for energy reasons? https://support.apple.com/en-us/HT204666