I use the same motion detection cameras as Alec, probably. It's set to start recording when there is motion. They are more used in areas where people are likely to mess with my stuff and run, like garage/driveway. Then just an alarm system...for the windows/doors and so on. Then an ak47 with 30 rounds to send anyone who gets in, away.
It's pretty basic, but I plan to go with a much more advanced system w/home automation after I move...I'll be in a gated community, so probably wont need it too much, but security is the coolest.