Oh the convenience of not having to use keys—that's what you get with a Bluetooth-enabled mobile phone and BlueGuard, the automatic door opener.
The $US200 unit detects up to 10 separate mobile phones at up to 10 metres (standard low-power Bluetooth range), and hooks up to the door-opening system to enable you to get hands-free entrance. The site says this is more of an industrial use, and attaches to "gates, overhead doors and parking barriers," so it's less of you getting into your home. Still, it's quite useful. [EMXinc via Wired]