FireFound is an add-on for Firefox that helps you find your computer if it's lost or stolen. Every time your computer's location changes, FireFound sends a secure message to a central server with its current location. You can then log into the server and see your computer's current location.
All of the location data is encrypted, so no one can find out where your computer is without your password.
If you lose your computer, you can tell FireFound to clear your personal data (saved passwords, browsing history, etc.) if anyone starts Firefox before you can retrieve it.
You can even run your own FireFound server; all of the code is open-source.