A couple of entries on Slashdot caught my eye yesterday. The first pointed to an article on something called celldar whereby signals picked up by cellular transmission towers can be used to track things on the street, such as people and cars whether they are carrying a cell phone or not. The second one pointed to an article about robots doing martial arts.
 
Put the two together along with a little bit of GPS, and you've got a mechanized tracking and acquisition system that requires little human intervention. The human agent identifies the target and locks the celldar in. The celldar transmits a stream of location data to the robot, based on GPS coordinates. The robot moves in response to the celldar transmissions and when within range, fires a disabling round at the target.
 
The robot sensors only need to be able to determine obstacles that impede mobility. The robot does not need to have sophisticated target recognition capability, because this task is handled by the celldar.
 
Now, combine this with a total information awareness database, and welcome to Minority Report.

Some more on surveillance, from Bruce Schneier.