All these things need to be done before laptop is lost or stolen but work quite well.
Some bits of software that should sent you enough infromatio if your laptop is is lots or stolen.
//www.ihoundsoftware.com/ Tracks your device and works with ipod, memory stick. Also quite nice with google map of where it estimates where your laptop or device is, just ok in Ireland.
//logmein.com/ Can tell you if your laptop is online or not and then you can login to machine and find out what person is doing on your laptop.
//preyproject.com/ Have not tried it but seams to have got great reviews.
//adeona.cs.washington.edu/downloads.html Open source option allowing you to track laptop and send you picture using inbuilt camera to your email.
Highly recommended that that if you find your laptop or know who stole laptop do not try to get it back yourself get the proper authorities involved.