We toyed around with some ideas a while back as well.

The biggest problem we couldn't solve was the "detection" part of the equation. What is the range of the sensors? Do you use motion? Invisible beam? Transponders? How much of a gap do we set between the sensors and the pylon/plane? Are there other things that might set off the sensors? If we fly 3 or 4 man up how do we differentiate?

A good idea but lots of bugs to be worked out.