While TrackingPoint released their self-aiming PGF rifle just last year, a slightly similar, if less deadly, consumer-level technology has been available for quite some time. For years, paintball enthusiasts have been hacking together self-targeting paintball sentry guns, which not only track targets, but light them up without you needing to bother to pull the trigger. In this video from several years ago, a nice, frosty bottle of beer is placed on a table. Joe is across the yard and he's thirsty. The only thing standing between Joe and the beer is a paintball gun in Auto Sentry mode:

Of course, the real question on everyone's mind is if this system can stop an intruder using multiple trampolines in your backyard:

The guys behind this system, by the way, have their website here.