Can you take your laptop with you at the end of the day? Or lock it up if no one else is around in a locked drawer?
There's an app I think I remember that will set off an alarm if the screen is locked and the magsafe is disconnected.
http://www.macupdate.com/app/mac/39997/plugspy
There's little difference between unplugging the magsafe and clipping the cable with cutters, and this way it makes a noise.