This is based on my published paper on WatchMI: Pressure Touch, Twist and Pan Gesture Input on
Unmodified Smartwatches.

It use accelerometer and gyroscope in a clever way, so that it allows pressure touch, twist and panning the watch face without requiring external hardware like pressure sensor.

For more information, check my website http://hsyeo.com and also the video http://bit.ly/watchmi
Or read my paper: http://dl.acm.org/citation.cfm?id=2935375

I also open source the code at github: https://github.com/tcboy88/WatchMI