The Sky Drone folks have an Indiegogo campaign selling Sky Drone quadrotors equipped with a digital, HD first-person viewing (FPV) camera system that operates over 3G or 4G. One advantage of this technology versus regular old analog RC is that your range is limited only by local cell towers; the only ground equipment you need is a smartphone or tablet. The feed is encrypted as well.
If you look at the prototype (to the right) you can get a sense of how the system works. A BeagleBone Black controls a USB camera module and communicates with the smartphone with the help of a cellular modem.