Randy Green is in development of iAlertU, a utility that takes advantage of the motion sensor built into the MacBook Pro to sound an alarm when someone picks up the computer. A demo video linked to from his blog shows the software being activated with the Apple Remote, making a sound similar to a car alarm being turned on, and then sounding a warning when someone tries to grab it.
The utility is currently in the alpha stage of development, and Mr. Green is taking suggestions through his blog. Heis expressed an interest in supporting iBooks and PowerBooks with built-in motion sensors, and he responded positively to a suggestion that the software use the MacBook Prois built-in iSight camera to snap a photo of the person trying to nab the computer and then email it to the owner.
No word yet on pricing or a release date.