Introducing visual processing on multiple moving robots brings the problem of understanding action to a very real, grounded domain in which real-time processing and reaction are crucial. This highly dynamic domain has pushed us to rethink our notions of vision and develop new ideas and strategies. It merits a great deal more attention by the vision and robotics communities. Two people meeting here is suspicious. All sorts of simple analysis, pattern recognition stuff can feed this.
Deliberate angle helps a lot.
There is a lot of activity at this military base, take a look at it. If only a few activities can occur this is easier. Crime is invariably at or near the top of every poll of public concerns, and demographic trends suggest that the rate of crime will begin to rise soon after several years of decline. People are willing to pay for security. This is despite the fact that current systems are only marginally effective, and are extremely prone to false alarms.