Oh man that stinks. Do you know how I would go about doing something like that? I've seen people with uav planes that have it.
If you're planning on building a UAV, then you are going to want something that can transmit the video real-time, at the highest frame-rate possible (especially if you intend to control/steer the device via what you see via the video). Unless your UAV is fairly large, this is generally going to mean going with a 2.4 GHz video transmitter and a small camera. Depending on the range you plan to cover, you may even need to figure out a method to use yagi antennas (or similar high-gain and directional antennas) on both ends, with full position tracking (based on the lat/lon cordinates from GPS on the plane, and lat/lon cordinates of the base controlling station). Control information to the UAV would be handled via standard radio-control gear, information back from the UAV, depending on density, could either be interleaved on the v-blank of the video signal, or sent over a separate channel (x-bee, or some other RF means).
A similar type system could be built for a UGV (unmanned ground vehicle), and may be preferable if the vehicle is smaller (and doesn't have the battery power for a larger system). Otherwise, if the UGV is large enough to carry the batteries needed, you could put a 802.11 g/n router on the robot, and communicate with the Arduino via an ethernet shield or similar, or connect the router to an on-board PC motherboard, and communicate with the Arduino via USB. In addition, your camera options expand greatly - HD firewire cameras, or USB cams - even network IP cams - all are possibilities. You could have such a system on a UAV, too - but such a machine might have to be fairly large to carry the gear (an option there though might be something like the BeagleBoard, or some other small embedded Linux PC).