Mark Gurman, reporting for that site that hasn’t retracted The Big Hack story:

Apple Inc. is said to be testing a sleep monitor for a future version of its smartwatch, a feature that would bolster the company in the health- and fitness-tracking market.

The company has been using the sleep-tracking feature for several months with testers at secret sites around its Cupertino, California, headquarters, according to people familiar with the work. If the functionality is successful in the testing stages, the company plans to add it to the Apple Watch by 2020, according to one of the people.

I’m curious how they’ll go about this. My Series 4 Apple Watch can easily go for two full days without needing a charge. Will they drastically increase battery life? Will they add be some sort of low power sleep mode? Anyway, this is one feature that I am waiting for.