Interesting, I hadn't thought about this one. I just looked it up and didn't realize that they already have an app for blood oxygen, though it isn't continuous:

Interesting, I hadn't thought about this one. I just looked it up and didn't realize that they already have an app for blood oxygen, though it isn't continuous: https://support.apple.com/en-us/HT211027 https://support.apple.com/en-us/HT211027