A GPS tracker for a car is either freestanding or designed to plug into the OBD-II port. A freestanding car GPS tracker can be put anywhere in or under the vehicle. A plug-in GPS vehicle tracking system attaches to a special port called the OBD-II ("on board diagnostic") on the driver's side, typically under the steering wheel and slightly to the left. You may need to remove the plastic dash cover to access the OBD port.