Hunting around for cool laptop security, I found the DontZap and VTSysReq/DontVTSwitch (v4.2/v4.3) options for X, which prevent people from using CTRL-ALT-Backspace (crashing your X), and CTRL-ALT-Fn (switching to another vty).
Nirva wrote a nice basic X locker.
This just prevents people from screwing lightly with your laptop. They could always just steal it. Hopefully, lockdir will have run before they make off with it.
If you have any laptop security suggestions, write me! ;)