For those of us in the USA, there is a MJFF study that will pair a Android Smart Phone and Pebble Watch. While I don't wear a watch anymore, I will be wearing one as part of this study!

Cool tear down on the watch is posted by eevblog Dave. Cool tech stuff.

One of the biggest issues when designing with accelerometers is drift. First part I played with drove me crazy as the data was great for rapid deceleration (air bag trigger) yet when tracking across time it seemed to really get odd data.

Sensor Fusion on Android Devices - TED talk 2010 on Youtube - give a good insight into the port processing math required when using an accelerometer.

The MM7150 Module has the Bosch Sensors on it, in addition to a processor to handle sensor fusion. This is what I was planning on using, but the pebble watch provides the same functions and is a cool watch.