Insert Coin semifinalist: Smart Knob brings keypad access to your front door

Keys? Who needs keys? The Smart Knob is an attempt to do away with those pesky metal things for property managers and renters, attaching a keypad to your front door's deadbolt. Owners of the property can issue codes remotely for a chosen period of time. Visitors can also get codes by calling the service's automated phone system. The Smart Knob is compatible with all standard circular deadbolts, and its creators insist that the installation process takes under a minute. The battery should last "up to two years" with daily use -- and when it gets low, a warning will let you know.

Check out a video of the original plastic prototype after the break. The final version will, thankfully, be made of metal.

Check out the full list of Insert Coin: New Challengers semifinalists here -- and don't forget to pick a winner!