Bring your home into the 23rd century without costly renovations with this motion sensitive Star Trek-inspired door chime from ThinkGeek. It's like being on the Enterprise, without having to worry about attacks from those pesky Klingons every other day.
You can mount it on either side of a door in your home, or every door since at $30 it's not terribly expensive, even for non-Trekkies. Then, whenever someone crosses the threshold that familiar whooshing sound of the doors automatically opening in the original Star Trek series is played. Or, if you suspect it's a foe and not a friend entering, it can also be set to sound the red alert alarm.