I recently purchased a Parrot AR.Drone: http://ardrone.parrot.com/parrot-ar-drone/usa/
It runs off WiFi, and I have already made my own API to interface to it using the packets described in the system developers manual. I wish to interface to it via 3G (if the WiFi signal runs out of range). This is for a number of reasons but I suppose the most compelling one is range (and I am well aware of the latency issues here, but it's a compromise i would be willing to accept for the range), the other day someone else I knew who had the Drone lost it by flying it too high over an urban environment and letting the wind take it, a 3G backup interface would've been a blessing here. Being an iOS programmer I first wanted to simply put an iPhone into the hull of the Drone and interface to it that way, and take advantage of the iPhones GPS, magnetometer, gyro, accelerometer etc, however it weighs too much, so to get started I would like to create a bridge between a 3G connection and the onboard WiFi connection, and further down the track I would like to add Accelerometers, GPS, Magnetometers etc for more autonomous navigation.
Given the lightweight of 3G hotspots I don't see this as a terrible solution, especially if I get rid of the battery in them and make them use the Drones internal battery. However this would mean I would need 2 WiFi peripherals (presumably 1 for interfacing to the Drones WiFi, and 1 for interfacing to the 3G's).