Robots are going to do many things for us, including patrolling our properties. In fact, there are already a bunch of security robots on the market. Nimbo from Turing Video is powered by Segway Robotics. It is pre-programmed to monitor specific routes.
The robot can detect security violations and uses light/audio/video warnings to respond. It also collects video evidence and sends your security personnel notifications. The robot can fit in small spaces and patrol campuses and warehouses.