1. A system comprising: a computer, a means for communications, and a camera that produces a multitude of scene images; a target storage module storing a target descriptor; a target recognition module running on the computer; an alarm module that causes the communications means to transmit an alarm signal upon receiving a recognition signal; and wherein the target recognition module obtains the scene images, obtains the target descriptor and produces the recognition signal upon discovering that any one of the scene images contains a pattern matching the target descriptor.