The MHA, a Kentucky-based software company with a name that can be tough to work into sentences, released Airlock on Tuesday. Airlock unlocks your Mac when you approach it, and locks it again when you walk away, using the magic of Bluetooth to detect your proximity by looking for your iPhone (or later-gen iPod touch). Always assuming you don't forget your phone at your desk, of course.
The developers at The MHA are smart cookies. If your iPhone battery dies, you can always type in your password to unlock your Mac. (And since you'll be leaving Bluetooth turned on all the time, you can of course expect that iPhone battery to drain even faster than normal.) Airlock works its magic via a System Preferences pane that offers a host of configuration options: You can set the distance range you must exceed to be considered away, as well as specific actions to trigger as you come and go—logging into iChat, snapping a photo, or loading a specific Website.
Airlock costs a palindromic $7.77, and a free trial is available at the The MHA Website. (See, I told you that name could be tough!) In addition to a Bluetooth-ready iPhone or iPod touch, you'll need an Intel Mac running Mac OS 10.5 or later.