I finally made it happen it reads to the cm!!
parts used :
fc: pixhawk fc
laser: sf11/c
http://www.lightware.co.za/shop/en/drone-altimeters/51-sf11c-120-m.html
osd: Alceosd 0v3
http://www.satxo.com/shop/index.php?id_product=8&controller=product
Its pretty well documented on how to set-up...