Rather than try to stop a theft, try to prevent it. One lock expert told me the only security cable he uses comes from PC Guardian--he opts for their combination lock, which he was unable to pick. (He taught me by phone how to pick combination locks offered by other manufacturers, which took me about 45 seconds the first time I tried it using an inobtrusive pick.)

You can also opt for tracking software. CyberAngel Security offers a package that can protect your data transmits an alert. They partnered with Skyhook so that a Wi-Fi connection will allow the laptop software to send an approximate location using nearby Wi-Fi receivers as both locators and conduits.

Slappingturtle.com has just released a beta for Mac oS X users that can turn a MacBook Pro (the new Intel-based model) into an alarm system using the built-in iSight camera, infrared remote control, and other tools. Ultimately, they hope to let the system upload a photo snapped when security is violated.