A vehicle accessory can transmit a first signal to a mobile device, the first signal including a location of a vehicle. The mobile device can monitor its own location. The mobile device can assess whether one or more location-based criteria have been satisfied based on the location of the mobile device and the location of the vehicle. Upon determining that a location-based criterion has been satisfied, the mobile device can transmit a second signal to the vehicle accessory indicating that a function of the vehicle is to be controlled. Thus, for example, the mobile device can activate or de-activate vehicle features (e.g., door locking, vehicle defrosting, etc.) in a manner that capitalizes on efficient signal transmission.