The new Apple Watch will now measure your blood oxygen level

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 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.