Windows: LAlarm uses the USB port or power port of your Laptop as a sensor to detect when your laptop has been disturbed.
While a piece of software is no substitute for keeping your laptop directly in your hands at all times, when it isn't immediately practical or convenient you can use LAlarm to give you a heads up if your laptop is on the move.
Once installed you can set LAlarm to perform a variety of tasks if your laptop is unplugged from its power cable or the wall, or if the USB drive—which you would need to use a strap to secure to something—is removed from the USB port. What task it will perform is up to you. LAlarm can sound the alarm, literally over your laptops speakers, launch applications, delete files, or recover them. In recovery mode critical files can be sent to you remotely if the thief uses your laptop.
Have your own favourite application for laptop security? Let's hear about it in the comments. LAlarm is free for personal use and available for Windows only.