Apple has posted their Human Interface Guidelines (HIG) for Apple Watch:
Personal. Because Apple Watch is designed to be worn, its UI is attuned to the wearer’s presence. A raise of the wrist shows the time and new alerts. Digital Touch–particularly its Heartbeat and Sketch features–enables new types of personal communication. An accelerometer and a heart rate sensor provide personalized information about the wearer’s activity from day to day. No other Apple device has ever been so connected to the wearer. Be mindful of this connection as you design apps for Apple Watch.
Just as the iPad marked the beginning of the “Post-PC Era”, the Apple Watch is marking the beginning of the “Post-Smartphone” or “Smartphone+1” Era.
The smartphone might still be the star of the mobile computing show, but it now has to share the stage with the tablet and the watch. Wearing a watch that’s tethered to your phone changes the relationship of how you interact with both of these devices.
Digital designers, UI designers, UX designers, web designers–I don’t give a fuck what you call yourselves–you best familiarize yourselves with the Apple Watch HIG.
It doesn’t matter if you hate the Apple Watch, or love the Apple Watch or never plan to wear one. Not making an effort to understand wearables will put you at a severe disadvantage as a designer.