Apple is introducing a new requirement for all Watch apps submitted to the App Store: they must be native apps built with the watchOS 2 SDK or higher.
The change will be coming into effect on 1 June, and should mean faster and more reliable apps – loading times and launch problems were two of the issues addressed by the second version of the SDK – as well as a wider feature set. watchOS 2 introduced haptic feedback for apps; access to the Healthkit sensors and accelerometer; and 'Complications', time-based notifications that appear on the clock face.
Perhaps the most important change, though, is that all apps will have access to 'WatchConnectivity', which enables the Watch to be used without a paired iPhone – at least temporarily – and connect directly to wi-fi networks.
With Apple's WWDC event just around the corner, this could hint at the next set of announcements for the Apple Watch. That looks most likely to be a new version of the SDK, but it could potentially mean a whole new device.