Texas TV station KPRC Local 2 has caught Houston police red-handed - test-flying an Insitu ScanEagle UAV. You can read the report and see hidden-camera video here. Despite staging the tests over ranchland 70 miles from Houston, Plod's cover was blown and they had to fess up at a press conference later in the day.
US police are champing at the bit to get their hands on UAVs, which they see as a cheap alternative to helicopters. At least one police department has already bought one only to be stomped on by the FAA, which takes a dim view of unregulated UAV operations in national airspace.
Demand is such that the US Department of Justice in October issued a bulletin to law-enforcement agencies cautioning them that UAV operations are regulated by the FAA. It makes clear FAA rules do not allow UAVs to be operated over populated areas. This might limit their usefulness, but KPRC does note the speed cops were spotted at the Houston demo.
According to the DoJ bulletin, Houston is the location for one of two FAA-sanctioned test projects intended to provide insight into operating UAVs in urban areas. The other is Miami-Dade in Florida. These could lead to a rule change after 2010. So the flying panda car may not be too far away.
(Okay, I know it's an Aerosonde, not a ScanEagle)