This bike computer project implements a complete bike control system, So instead of pulling a steel cable with a shifting mechanism, you can change gears electronically. The shifting of gears is controlled by a small bicycle computer, so the bike is always in the right gear.
The new electronic gear shifting system is controlled by a pair of servos with push buttons in the handle bar. This allows to automatically trim the bike chain, in order to completely eliminate chain rub.
The bike control project also adds GPS, accelerometer, an altimeter and a heart rate monitor and pulse ox meter. You can pick up the current version of the design over on GitHub and follow all the updates on the author’s blog.