Another option, which I'm considering for my new Macbook, is LoJack for Laptops, which is just what it sounds like. They finally released a Mac client in July, though there are some privacy questions associated with them (such as, just how much can they see on your hard drive, and just how easily is the software removed). Essentially, the lojack software checks into a central server whenever the laptop connects to the Internet, so the computer can be tracked if it is ever stolen. Perhaps someone else on here has used it?