https://techcrunch.com/2019/09/03/the-next-apple-watch-could-feature-sleep-tracking/

Details have surfaced about one of the potentially key features of the next Apple Watch — sleep tracking. Bloomberg originally reported that Apple has been working on a sleep tracking feature, and 9to5mac now details how the implementation could work.

The new feature would work on the next Apple Watch. The new device could be unveiled at Apple’s iPhone event next week or at a later event this fall. It’s unclear whether existing devices will also support the new feature.