I managed to fly one N900 using kites, for KAP (kite aerial photography). It was attached to the line of the kite in a rig with two servo motors (for pan and tilt). The servos were controlled by and Arduino with a Bluetooth modem, which received the pan/tilt commands from the N900. It also streamed video to another N900 on the ground, which in turn sent pan/tilt commands (created using just the accelerometers, by tilting the device) to the N900 on the kite. The Wi-Fi signal (in Ad-Hoc mode) was very good for about 150m, but after 160m or so, some video frames were being lost. For KAP purposes, the video was still good enough for about 200m or more, but I would never even try to control a model aircraft with an N900 beyond 100m! A router with more power and a good antenna could get you a wider signal range from the ground to the device on the aircraft, but it might not help as much the other way around...

This project was part of the Nokia Push contest. You can see the official blog for more information (under "More KAPing with the N900 Updates"). There is also a set on Flickr with images (and even some code) from the project.