Here’s a free tool called Bezel that allows you to project WatchKit apps running in the simulator into a WatchKit styled app so you can get a better idea of how your apps will look on the Apple Watch complete with Bezel.
Bezel uses an artists rendering of he Apple Watch, and can use other watch frames with some extra images provided.
Be sure to go through the readme included with Bezel for further tips on simulating WatchKit apps.
You can find Bezel over on the homepage.
A nice tool for those working with WatchKit.