(Yes, you can!) With the WatchKit SDK you can enrich the Apple Watch experience with Estimote Stickers. The demo, Sneaker Seeker, is a simple hot and cold game based on ranging. The entire code is available on GitHub.
Currently, it works only with Estimote Stickers. You can easily simulate entering/exiting a region and moving across all three proximity zones (Far, Near, Immediate).
We published an introduction to Estimote WatchKit SDK on our blog.