Update March 5, 2014
Johann designed a new concept to calibrate. I think its better than this one, because it doesn't needs mechanical parts.
http://reprap.org/wiki/FSR
https://groups.google.com/forum/#!topic/deltabot/6fxnM20nYKc

This is my Automatic bed leveling probe for my new Kossel. It works at the Kossel and also at the Rostock-Printer with the Firmware from Johann. More Information about Autoleveling:
http://reprap.org/wiki/Kossel

More Information about my Leveling-Probe:
http://6brueder.wordpress.com/2013/10/20/klapptaster-vorteile/

A video about the functionallity:
http://www.youtube.com/watch?v=eXu27z3Sgg4

9-12-13
Now also for 10mm longer Hotends.

-For the microswitch i use M3 screws instead of the M2.3-
-This are my functions in the Firmware from Johann for deploy and retract the z-probe.

void deploy_z_probe() {
feedrate = homing_feedrate[X_AXIS];
destination[X_AXIS] = 30;
destination[Y_AXIS] = 75;
destination[Z_AXIS] = 40; //NB vorher 100 für Kosselumbau reduziert
prepare_move_raw();

feedrate = homing_feedrate[X_AXIS]/10;
destination[X_AXIS] = -10;
prepare_move_raw();
st_synchronize();
}

void retract_z_probe() {
feedrate = homing_feedrate[X_AXIS];
destination[Z_AXIS] = 40;
prepare_move_raw();
feedrate = homing_feedrate[X_AXIS];
destination[X_AXIS] = -35;
destination[Y_AXIS] = 75;
destination[Z_AXIS] = 40;
prepare_move_raw();

feedrate = homing_feedrate[X_AXIS]/10;
destination[X_AXIS] = 12;
//destination[Y_AXIS] = 82;
//destination[Z_AXIS] = current_position[Z_AXIS] + 30;
prepare_move_raw();
feedrate = homing_feedrate[X_AXIS]/2;
destination[X_AXIS] = 0;
destination[Y_AXIS] = 0;
destination[Z_AXIS] = 40;
prepare_move_raw();
// Move the nozzle below the print surface to push the probe up.
//feedrate = homing_feedrate[Z_AXIS]/10;
//destination[Z_AXIS] = current_position[Z_AXIS] - 14;
//prepare_move_raw();

//feedrate = homing_feedrate[Z_AXIS];
//destination[Z_AXIS] = current_position[Z_AXIS] + 30;
//prepare_move_raw();
st_synchronize();
}