Hey @tsugua. No actually for this I'm not using artnet. The DMX is being generated by a Chamsys MagicQ console, and the WatchKit app is communicating with this via Chamsys's CREP protocol. Check out their manual for more info if you're interested. I'll definitely be sharing a gem for CREP at some point.
I have wondered about using ArtNet in my own apps at some point, but so far I haven't found a nice Objective-C library for it. Also I'm not convinced it would work very well from a watch app as the code would only be running whenever the app is visible, which doesn't appear to be for very long durations!