While I prefer to use a long password to protect my computer, I like the idea of being able to use a physical key to lock it. This is precisely what Airlock does, using your iPhone. It works great.
Airlock is a system preferences pane. Double-click to install it, associate it with your iPhone or iPod touch, set the security range, and that's it. I tried with my iMac 24 and my iPhone and it worked perfectly. You can even see a radar screen showing the distance between the two devices. The moment I stepped out of the limit, the screen locked. And then, as soon as I came into the perimeter, it unlocked automagically.
There is only one problem: If you use a wireless mouse or keyboard, it won't work due to a Bluetooth bug in Mac OS X. Otherwise, this thing will make you feel like James Bond.
Without the Aston Martin. And the Martini. And the laser watch. And the Scottish accent. And the hot girls. OK, so it won't really make you feel like James Bond, but come on, get on with the program here.
(Via John Gruber.)
I've been using Airlock at work for 2 days now and am loving it. Before, I was being lazy and not locking my computer when I step away from it, which is bad because I'm the webmaster and have access to...well everything. Now, It does it for me, automatically, when I leave my workstation. This utility is a really seamless and elegant solution. Also, if I ever leave my iPhone at home, I can still log in via the login/password prompt when needed. Another note - I HATE the ugly blue and black striped bar that is displayed on your screen when your computer is locked. I wrote the company that makes this App and they responded promptly saying that they've received a lot of feedback and that users should look for more lock options in the next version (screensaver, etc). More screenshots: