Pebble's first round timer for exercising/boxing/martial arts/stretching/yoga. You specify how long you want the round to be, if you want a round ending warning (defaults to 00:00), and how long you want your rest to be. Then it counts those through and buzzes to tell you when to switch.
It works, but I do have a few plans for making it better. For one, the lap interface that Katharine has for the stopwatch is still in there, but it doesn't make sense for a round timer.
I wanted to share my progress with everyone and solicit some feedback. I feel like the config screen is a little clunky (especially because you have to press up or down to activate the start button) and I don't know what to do with what is currently the lap button when actually counting down.
I plan on also putting text on the screen to tell you what part of the round you're in. Possibly with black, grey, and white backgrounds for quick glancing.
Update 2013/04/26:
Version 2.2 released! Added total time and made the vibrations all unique so you can figure out which round you're in without having to look at the watch.
Screenshots and file here.