Ask HN: any developers making apps for wearables?

In particular, motion tracking wearables like wrist bands and watches. Examples are FitBit, Jawbone, Pebble, Kiwi, etc.

I want to know what your experiences have been so far, but I'm also very interested in why you might have not started developing on wearables. E.g. is it because there's too much fragmentation and you don't want to make an app for one device that's going to fail, and then try rewriting for another device that could fail, etc? Do the devices and API platforms currently not provide enough to do useful things with? Is there something you wish existed for these wearables that currently doesn't?

Cheers