http://preyproject.com/

There are tons of features in Prey:  (LATEST NEWS - will now protect your MAC, LINUX and ANDROID Phone)

• Uses Wifi hotspots or GPS embedded in the device to accurately pinpoint where the laptop is.
• If Wifi isn’t in use, Prey will try to auto connect to an open hotspot to send you info.
• Prey is written in Bash and very lightweight. It’s also Portable!
• You can edit Prey as you like, adding or removing specific tasks, because each task uses a different module.
• Prey will list running programs and any files that were modified, as well as take a picture of the person if you have an integrated webcam.
• Messages can be sent to the device to be read on the screen, and even heard by anyone nearby.
• Last but not least, Prey is open source and FREE for up to three devices, and will run on any laptop.

First, download Prey onto the computer that you wish to track. Click on download and go thru the installation wizard. The download takes barely any time at all and at the end, if you havent configured the tool, it will prompt you to do so.

First thing I need to choose is setting up my reporting method. You have two options- you can either use a control panel interface, or a standalone interface. The difference is, the control panel can be accessed thru the prey website, and is quick and powerful- everything get sent directly to you as the reports come in. The standalone version will send you updates in your email, but to activate Prey to start reporting you need to activate and delete a URL and setup your mail server settings by hand.
Choose the control panel version. You need to create a new user account so type in your name, email address, and password. Change the name and device type. Click Create.

You’ll need to activate your email address, so log into your email, click the link and log in then add devices. Go back to the install and click OK and it tells you congrats now your devices are being tracked!
Now add a device by clicking the orange button. Fill in the name and it generates all your information about the device. Click create and it’s created. It gives you a device key and you can click on the name to configure all your settings. All of these choices are pretty self explanatory and if you don’t know what you’re choosing, hover over the exclamation point and it’ll explain the setting for you.

Now, if your computer gets stolen, log into prey project.com and change the status to missing. Now, updates will be recorded on your prey project page for you to view every 20 minutes (or however many minutes you choose).

Most Text and info from HAK5.org