iAlertU normally sounds an alarm when your 'book's motion sensor is triggered, which in itself is a deterrent, and snaps a picture of the thief - but the picture is just stored in your home directory making it useless if the thief takes off with you 'book. By scripting that snapshot to be uploaded to an FTP site (or even emailed to you), you have a mug shot to bring to the cops or post on the cafeteria bulletin board and may stand a better chance of catching the creep. Check out the full article for all the details. While Adam himself points out that there are probably slicker ways to accomplish this, his method is fairly simple and he does a good job explaining it all.
On a related note, the developer of iAlertU is currently seeking donations, by way of a random drawing contest to win $100, in order to buy a new Macbook since some of the features of iAlertU work fine on his MacBook Pro, but seem to break on a MacBook, which he explains is the reason for the slowdown in the development cycle. You can enter the drawing for a buck and if you want to see the app progress, it might be a worthwhile investment.