I grabbed a banglejs a while back for cheap embedded funzies, and it's really stellar as a hackable companion device that you don't use much, or at least in fairly passive or niche ways. Espruino is really cool though, and that's the heart of the project.

I wonder how this compares as a higher-end (maybe only other?) FOSS watch, mostly on the battery/power ratio. I actually don't know much about the pebble design.