"This summer, I'll try an IP HD camera connected to an Ubiquity wifi antenna. It should do the work..."

"Did you looked at the Xbee technology or similar rf equipment?
http://www.digi.com/products/wireless-wired-embedded-solutions/zigb..."

"I used a CMUCam2 (http://www.cs.cmu.edu/~cmucam/) on a UAV project 3-4 years ago to do a similar task. It's relatively expensive (200-300$), but it's really fast and efficient to track color objects or movement and doesn't need to do the processing…"