https://techcrunch.com/2017/09/12/apple-watchos-4-with-better-heart-rate-monitoring-arrives-september-19/

The updated software powering the Apple Watch, watchOS 4, will be released on September 19, 2017, for all Watch customers, according to Apple COO Jeff Williams, speaking at Apple’s iPhone press conference today. The updated software, which includes features like new watchfaces, improved fitness coaching, a redesigned music experience, and more, was previously announced this summer at WWDC.

Some of the biggest changes in the new watchOS have to do with its health-related features, for obvious reasons. Apple vaguely referred to the Apple Watch as the ‘most used heart rate monitor’, but didn’t offer a source for that data, for example. But Apple Watch, like most wearables today, attract many users because of their their health monitoring and fitness features.