Aerial Photography
I've been trying to decide what sort of hobby project I'd like to work on next. Remote applications have fascinated me for a long time, and it seems to be a really hot area right now given the growing popularity of 802.11 wireless.
I think that it would be really cool to take photos from a remote-control plane. There are a few people who have already done this, and published the process for others to learn from. Unfortunately, their instructions refer to an outdated camera model, and don't transmit images in real-time. X10 cameras might be able to solve this problem, but I'm not certain of their image resolution or signal strength.