If you're interested in exploring WatchKit, check out @NatashaTheRobot's write-ups:
It's interesting - there are so many constraints in creating Apple Watch apps. The constraints are well-chosen - they'll help enforce better ergonomics as we all adapt to designing for a new platform, and will prevent battery drains.
Try downloading the SDK and play around with it - yes, the constraints are pretty strict, so try and focus on your designs above and outside of the watch itself - where is this device being used? How? Why? That kind of larger design, along with an understanding of the constraints, will be super valuable as you approach designing for this new platform.