High end Samsung phones and some Garmin watches have pulseox sensors too. They're not super accurate, but better than nothing. Some Apple phones have them too, but they aren't accessible unless your phone is jailbroken and you have an app to get to them.
A nice, thought-provoking piece from Jaron Lanier and Glen Weyl re data labeling as slavery/barter, AI more generally, personal data sovereignty, and AI as authoritarianism. With a dash of delegative democracy thrown in.