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InfoQ Homepage News Apple's watchOS 2 Introduces WatchKit Apps and Extends Hardware Support

Apple's watchOS 2 Introduces WatchKit Apps and Extends Hardware Support

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At WWDC 2015 Apple announced watchOS 2, which brings new features and capabilities for apps "to integrate even more closely with Apple Watch" by allowing access to the Apple Watch home screen, digital crown, microphone, etc.

WatchKit Apps

The conceptual model for an Apple Watch app has not changed much with the introduction of watchOS 2. Indeed, third-party apps:

  • can only run when the watch is tethered with an iPhone.
  • come bundled within an iPhone app that provides the code for managing the WatchKit app’s user interface and for responding to user interactions through a WatchKit extension. Code can only run on the iPhone.

What is new with watchOS 2 is the introduction of WatchKit apps as an additional bundle that contain the storyboards and resource files associated with the user interface and that runs on the watch. WatchKit apps are bundled within the same iPhone app that contains the WatchKit extension and their main advantage is that they reduce the amount of communication between the iPhone and the Apple Watch that is necessary to display UI elements. This will improve overall performance. Also new with watchOS 2 is the possibility to have user launchable apps that appear on the watch home screen.


ClockKit is a new framework that allows developers to create complications for WatchKit apps. Complication is the horology term to describe any feature in a clock or watch beyond the simple display of time. Simply put, ClockKit supports apps that will update their information directly on the clock face throughout the day. This will open up the possibility to customize the appearance of the watch face. However, ClockKit complications need approval by Apple and they must use specific templates to ensure the look properly on all Watch faces.

Better integration with Apple Watch hardware

In watchOS 2, apps will have access to Apple Watch hardware components such as the Digital Crown and Taptic Engine, to allow the creation of apps that support more advanced user interaction. Furthermore, apps will also be allowed to access the heart rate sensor, accelerometer and microphone, thus opening up whole new categories of applications that were previously out of reach for third-party developers.

Developers can start using watchOS SDK right now, which requires the pre-release version of Xcode 7 and iOS 9.

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