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 new 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. For instance, watchOS 4 will introduce a new mode called “Gym Connect,” which allows you to sync directly with gym equipment like treadmills and ellipticals.
It will also include new heart rate sampling which provides a better resting heart rate measurement. That is, Apple Watch will now notify you if you have an elevated heart rate but don’t appear to be active.
The "Apple Heart Study" was announced, as well. This will utilize data from Apple Watch to monitor for arrhythmia. People will be able to participate in the study with Stanford by downloading an app from the App Store, Williams said.