In the past few weeks the oxymeter feature was enabled by a firmware update on series 10. Measurements are done on the watch, results are only reported on a phone.
As of September 9, 2025, hypertension notifications are currently under FDA review and expected to be cleared this month, with availability on Apple Watch Series 9 and later and Apple Watch Ultra 2 and later. The feature is not intended for use by people under 22 years old, those who have been previously diagnosed with hypertension, or pregnant persons.
I believe this is for the fringe cases where you have been diagnosed with hypertension, but your apple Watch does not tell you that you have hypertension risk, then you may decide to not take your drugs, since your watch told you all clear. This could trigger lawsuits if complications set in when you decide not to take your drugs because of "lack of alarm"
Then you get a new fringe case: you are not yet diagnosed with hypertension, but you are aware that your apple watch has that functionality so you decide you don't need to be diagnosed.
The point of the detection features are to notify people who are not diagnosed with the condition to go to the doctor about it possibly get diagnosed with it.
It's not useful for people already diagnosed because they already know they have it, so the notification is just telling them something they already know.
Going to be interesting comparing the series 10 blood pressure sensing against my Hilo (formerly Aktiia) band on the other wrist. Although without calibration against a cuff, I'm not super convinced the Apple Watch will give reliable information.
https://www.apple.com/watch/compare/?modelList=watch-series-...
In the past few weeks the oxymeter feature was enabled by a firmware update on series 10. Measurements are done on the watch, results are only reported on a phone.