Dig this. It's a piece of software that uses the harddrive motion sensors in the new macBook Pro to signal an alarm when it is moved.
Ordinarilly the laptop uses the motion sensors to lock the HDDs down in the case of a fall...but this is a pretty clever use for the equipment the rest of the time. It's also a pretty clever use of the new Apple remote included with your MacBook.
One glaring flaw that I see is that there is a MUTE button on the keyboard of the MacBook, which would easily limit the effectiveness of the alarm. However, it's not unreasonable that the software, when active, would disable the keyboard altogether, if not simply the mute button. If I were the maker of the software, I would make it disable the keyboard...because I don't need you jackin' with my crap! You hear me? Punk!