The new Apple Watch tracks blood oxygen, but how useful is this feature?

The new Apple Watch can be summed up in two words: blood oxygen. The ability to measure your blood’s oxygen saturation — an overall indicator of wellness — is the most significant new feature in the Apple Watch Series 6, which was unveiled this week and becomes available on Friday. (The watch is otherwise not that different from last year’s Apple watch.) The feature is particularly timely with the coronavirus, because some patients in critical condition with Covid-19 have had low blood oxygen levels.

But how useful is this feature for all of us, really?

I had a day to test the new $399 Apple Watch to measure my blood oxygen level. The process was simple: You open the blood oxygen app on the device, keep your wrist steady and hit the Start button. After 15 seconds, during which a sensor on the back of the watch measures your blood oxygen level by shining lights onto your wrist, it shows your reading. In three tests, my blood oxygen level stood between 99 percent and 100 percent.