Scared that someone may steal your car? Do you have car driver employees that spend their time in road coffee stops? Do you have a grandma with Alzheimer? Are you in any sort of situation that you want to track something/someone and reveal its position on google maps?
Here is a step bu step tutorial from Cooking Hacks team showing how to create a homemade GPS tracker. The design is based on Arduino and hosts a GPS+GPRS shield with an antenna attached to continuously pick up the location of the vehicle. Making a call to the Arduino inside triggers an SMS message to be sent back with the specific GPS data of where the tracker is stationed at. Information is then set to a server and inserted into a database, which can be accessed by opening up a specialized Android app.