The Sentry Gun

These two geeks have built their prototypes for an automated sentry gun. Now, anybody who has watched Aeon Flux knows that this is a bad idea. Their version uses webcams for tracking, along with a bunch of robotic servos and software to recognize a person. .

Of course, the technology has been around for quite a while to build this, but I think most people have, wisely, shied away from it.