The currently supported models are the Apple Watch Series 4, Series 5, Series 6, Series 7, Series 8, Series 9, Watch Ultra, ...

including the Apple Watch itself. New with the Series 6 is an integrated blood oxygen sensor. It works similarly to the ECG sensor. It shines a myriad of lights onto the back of your wrist ...

AliveCor has lost its appeal, meaning there won’t be another ITC import ban over the Apple Watch’s EKG feature.

but lack ECG. watchOS 11, the latest version of Apple Watch software, supports Apple Watch Series 6 and higher, Apple Watch Ultra 1 and higher, and the second generation Apple Watch SE.