Ars Technica:

All of the Apple Watch’s third-party applications so far have used WatchKit, a small SDK that limits apps’ functionality and UI and restricts them from using all the watch’s underlying hardware. At its WWDC keynote today, Apple announced that it would be moving beyond WatchKit and giving its third-party developers a more capable, native SDK that can take advantage of more of the Apple Watch’s features.

With WatchOS 2 and the native SDK, third-party apps will be able to do more of the things that Apple’s first-party apps can do.

This is a really big deal, akin to the launch of the App store the year after the original iPhone launch. It’s going to make the Apple Watch app ecosystem positively explode.