One doesn't really think of doors as being very high-tech. Granted, you do have some with pretty high-tech security locks and biometric scanners.. This doorknob doesn't have all of that fancy high-tech stuff inside it, but it does have a high-tech look about it.
The idea behind this doorknob is simple. Make an easy way to ensure that no one can enter a room, regardless of whether or not they have a key. The easiest way to keep someone out is to simply remove the doorknob itself. If you've got nothing to turn or pull on, the door isn't going anywhere. This is a great idea for someone that has a roommate that doesn't know how to take a hint.
You just pull on the inside knob and the outer one retracts. It does not appear to work in reverse, so you don't have to worry about getting locked inside your room. As far as I can tell, this is only a concept. Were this to make it to the production line, I could really see it catching on in the hotel industry. It's an easy way to tell the housekeeping service that you don't want to be disturbed.
The DoorKnob Condition Ensures Privacy [via ohgizmo]