A simple 2 DoF setup with an accelerometer (LIS302DL) attached to the effector. The seeeduino attempts to drive the servos so the Z and Y axis measure zero acceleration. The sketch is available at the usual place.
The algorithm employed is a simple PD controller with pseduo-gradient stepping to determine how to control each servo without any knowledge of how the servos are arranged. To deal with sensor noise from the accelerometer, a schmitt trigger mechanism is employed along with a moving average.
The code also allows the system to be calibrated to deal with accelerometer miscalibration.
It is cute, but that is about it :-) Coupled with a tripod and better construction ut might be useful for some DIY surveying or construction work.