Bought one of these last week and it works great.  I spent an hour trying to find my car one day at Disneyland because some girl said that she knew the Disneyland parking lots like the back of her hand therefore I didn't need to mark it with Google maps.  W hen you turn off the ignition your lighter socket should turn off.  My guess is that the Zus has a capacitor that holds a charge just long enough to send a signal to your smartphone via Bluetooth saving the coordinates to the Zus app.  See the Zus video at: https://youtu.be/wLY8G3P6l5g .  There's a app that claims to do the same thing without the hardware but it never was reliable for me.  Others I've talked to have had the same problem going the cheap route.