A WatchKit app requires an existing iOS app. The WatchKit app is implemented as a separate target of your Xcode project and is built and packaged inside your iOS app’s bundle.
- https://developer.apple.com/library/ios/documentation/General/Conceptual/WatchKitProgrammingGuide/ConfiguringYourXcodeProject.html#//apple_ref/doc/uid/TP40014969-CH2-SW1
- https://developer.apple.com/library/ios/documentation/UserExperience/Conceptual/WatchHumanInterfaceGuidelines/index.html
- https://developer.apple.com/watchkit/ (for design resources)
- WWDC 2015 416 Build Modern Frameworks