Ok so updates, first i have first pcb tests working ! using this method.
i opened a github project for this here https://github.com/Atntias/probz/commits/master
i wrote the code as a part of printrun. the code is very messy but its starting to work :).
im using a dilling head based on the mantis i designed to fit the prusa X carrige, wich i will shortly upload to a thing too.
This is based on few ideas i saw online to use and automated process in order to measure distances from head to bed on all the working area.
then you can take that data and use it to offset gcode accordingly.
this is critical for pcb milling, and nice to have in 3D printing, as the whole leveling process becomes not critical as it is.
gcode offset calculation differs from CMC milling to 3D printing, but im planing on developing both.
i can probe the surface by replacing the z end stop with 2 wires 1 goes to the aluminum bed and the other to the extruder nozzle/drilling head.
video of the probing in action http://youtu.be/tKFhiu2a64I
the pcb holder you see in the video is another thing il make soon.
yet to come...
note: you need to use marlin firmwre as it return endstop hits locations.
make sure in setting #USE_ENDSTOP_ONLY_FOR_HOMEING isnt selected.
right now when printing/milling i just disconnect the endstop, but il add a M code to turn the above #USE_ENDSTOP function on and off.
you might have to invert your z endstop nc/no in the firmware.
im using mayavi view to show the data, and numpy to do some calculation, so best way to get all that is get pythonxy instead of python 2.7.2 and make sure to select ETS on the packge list on installtion.