"Remote-controlled devices can easily be hacked to add Arduino-based control, thanks to the simplicity of the analogue and digital I/O pins - and many people now have Arduino remote-controlled cars and so on. However working with flying devices such as model helicopters and quadcopters can seem to be a little trickier, however with the right control system they too can be used.
One fascinating example of this is a quadcopter controlled by a Leap Motion with Arduino-based interface hardware. This system allows for control of the quadcopter with simple hand gestures - as shown in the following video:"