Code can be found at
Johan's (jcrocholl) Github branch
Here are some images of how the sensors are attached to the printer (under
the bed):
3D Printer 4 - Auto Bed Levelling
3D-Printer
hardware
Video of the G29 (Auto level) command.
This process involves using 3 Force Sense Resistors (FSR's) in order to use
the actual print head as the z-probe.