Nice write-up on the options and tinkering you can do with TI’s MSP430 Chronos watch. I got one of these a while back on sale. I haven’t found a good project for it yet, but this maybe a good time to re-visit it.
http://dangerousprototypes.com/2013/12/03/ti-ez430-chronos-watch-getting-started-on-custom-firmwares/
http://www.itopen.it/2013/11/28/the-hackable-watch-a-wearable-msp430-mcu/