Try using a ultrasonic range sensor pointed downward to get an accurate height. Though a microcontroller on the heli will be required.
http://www.sparkfun.com/commerce/pro...roducts_id=639
I don't know about amtel but I have been pretty successful with picMicrochips(go with 18 series so you can program smilar to the RC)
Can anyone explain to me the difference?