Thanko's new USB PC Lock does what you expectlocks your PCbut the real height of geekery is the accompaning receiver (that you're apparently supposed to wear on your shirt, yeah right). When activated, the computer will automatically lock up when you move more than two meters away from it (that's 6.5-feet in American). Thankfully, it'll also work if you put it in your pocket, which we recommend you do. Like, really recommend.
You can see how the lock looks like, at http://www.popgadget.net/images/pclockphoto%5B1%5D.jpg
This is an amazing feature a lot of people will benefit from. I am going to have to look into this more. I hope to see more like this in the future.