These techniques have actually been used to recover stolen MBs and MBPs and prosecute the scumbags who stole them. Video here.
Do you have a MacBook or MacBook Pro? If you do then you’re in luck, give iAlertU and TheftSensor a try [also see Undercover]. These two free applications take advantage of your MacBook or MacBook Pro’s Sudden Motion Sensor as well as other input information to activate a Security Alarm-like sound notifying you of intruders on your Mac.