This is auto bed-leveling sytem for Ultimaker. It will also fit derevative printers like Joysmaker or Dreammaker.
The main idea is to mount z-min endstop to the print head. It will probe 4 points of the bed before the print. All moves will be transformed according the bed aligment. Servo serves here to lift the probe up during the print.

Watch how it works: http://www.youtube.com/watch?v=x8eqSQNAyro

UPDATE 16.02.2014:
Use new firmware version
https://github.com/Bevaz/Marlin/tree/Auto_level_2.00
It allows to interactively set the extend and retract angles of z-probe via LCD controller. Also the probe will be extended only once during bed probing.

UPDATE 11.01.2015
Firmare synced with latest Marlin can be found at:
https://github.com/Bevaz/Marlin/tree/Auto_level_3.00