Reminds me of the automatic machine guns used in "Aliens", when the Marines were holed up in that one section of the base, they set up 2 automated guns that had radar which would lock onto anything moving and blast it. Really cool effect. Always wondered why we didn't see similar weapons (particularly with the abundance of 1st person shooter games - technology couldn't be that far behind).
First is the MULE UGV (Unmanned Ground Vehicle) which will have a gun/missle system in the ARV-L model.
Thes UGVs range in size from the small I-Robot Packbot to vehicles as large as a tank. Kinda like the "Bolos" from the Sci-fi books series. UAVs range in size now from papaer airplane dimensions with a small camera, to Helicopters, to the Global Hawk.