It's in the Apple PR https://www.apple.com/newsroom/2025/08/an-update-on-blood-oxygen-for-apple-watch-in-the-us/ https://www.apple.com/newsroom/2025/08/an-updat

It's in the Apple PR https://www.apple.com/newsroom/2025/08/an-update-on-blood-oxygen-for-apple-watch-in-the-us/ https://www.apple.com/newsroom/2025/08/an-update-on-blood-ox... > sensor data from the Blood Oxygen app on Apple Watch will be measured and calculated on the paired iPhone