Futurology

Sounds like this is to keep the citizens in a passive, compliant mental state, where they fear to do anything because it is out there watching at all times. If anything, it waits outside to prevent a thought from becoming a crime - "I see you leaving your door late at night to visit your neighbour's wife . . . again". It only travels at 7km/h, so it is not there to apprehend, only to deter.