An alarm is ok if you keep your truck in your driveway and you are home with it. If you can't babysit it, anyone with a flatbed towtruck could drag it away even if you had the thing on blocks.
Personally, I have a security camera in my driveway to keep an eye on things (my home computer takes a capture shot every second and stores it on disk). The security camera set up cost me about $200, $100 for the camera (it's pretty high resolution black and white with night vision from Clover), and $100 for the video capture card and 80 GB hard drive for my computer. It runs on an old 266 MHz machine I keep in my closet. I can read the license plates of anyone that drives by on the street.
I park in a very secure parking lot at work with 24 hour security, so things are safe there. I am thinking of getting a boot for the wheel if I decide to park it anywhere else (after I finish it and drive it more). You know, one of those big orange/yellow clamps the parking nazis use if you don't pay your parking tickets. One of those would make the truck pretty hard to steal.
