A GPS based car locator by msuzuki777, an instructable here:
The GPS continuously reads the latitude and longitude of the CarTracker. When the button is pressed, the coordinates are saved to the EEPROM. E.g., this would be the location of your car. Now, let’s say you walk out of a store and are looking for your car. Power up the CarTracker. Do not push button. The GPS will read the coordinates of the store and will calculate distance and direction from there to the stored location (of the car). The compass will orient the display so the display will point to the car and will display the distance.
Via Embedded Lab.