Not truly open, but we have an SDK similar to this that you can play with.

It works with any open accelerometer (Apple Watch, Android Wear, Microsoft Band, Pebble). We track 50 exercises, auto classify 22, and there's a machine learning tool that let's you add new movements to the system and improve it over time.

www.focusmotion.io

This is part of my honours thesis for my comp-sci degree. Once i've completed that, i'll definitely look at open sourcing.