Airlock allows your Mac to lock itself, plain and simple. Using your iPhone or iPod Touch, Bluetooth, and a smidgen of pixie dust, Airlock determines whether you’re near your computer. When you leave the room – poof! – your Mac locks itself. â€œAnd when I come back?â€ You guessed it: your Mac unlocks.
Of course when you’re without your iPhone or iPod touch for some reason you can log in the regular way. Just make sure the “Enable manual login” is clicked. A very nifty utility utilizing your iPhone as a security device. And just $7.77. Source: The M.H.A. via Joseph McLaughlin, Daring Fireball