For the type of aircraft suggested, I honestly think they are a long way away from utilising them, UAVs are far more likely, can be controlled far more efficiantly and can carry out the type of surveillance work currently done by helicopters without too much difficulty.
The remote controlled device you alude to cannot carry anything like the equipment required by the Police, whereas a helicoptor or UAV can.
As things stand, UAVs currently cost about the same per hour as helicopters, to my knowledge they are only operated by military organisations or on behalf of, and any costs involved to impliment them within the civillian sphere would have to met by the civi' organasations involved - ultimately the taxpayer.
I've no doubt that UAVs for Police surveillance work aren't all that far away, but until then, it will be helicopters and fixed wing.