Alongside its new beta of iOS 9, Apple has released the third developer beta version of watchOS 2. Developers will need the latest iOS 9 beta, in addition the to the watchOS configuration profile, which can be found the watchOS resource site.
When watchOS 2 arrives later this year, it will bring with it a number of improvements for the Apple Watch. Developers will be able to write apps that run natively on the watch, and take advantage of more of its hardware. Developers will also be able to build their own complications for watch faces that support that feature.