OK I should have seen this coming, the author has been busy working on building a dashcam system (2 cameras, GPS, etc) with an RPi. I like the RPi ignition sensitive power supply (below) the author uses. Thought at $20, I may just use a 12v to 5 volt converter with a fuse from the bread box instead. Especially since it seems it still takes juice from the battery even when off. Oh there has to be a cheaper GPS chip over adafuits $40 one that you can use.
http://pidashcam.blogspot.nl/
http://mausberrycircuits.com/collections/car-power-supply-switches/products/2a-car-supply-switch