I'm trying to find something that will turn on with the ignition, and store GPS data as I ride. Basically, I want to know where I have been - not where I am. I have searched for GPS trackers and all I can find are hidden, battery powered units, and ones that triangulate cell towers to give an approximate location. They seem to be geared towards catching a cheating spouse or companies tracking their drivers. I want a small box under the seat, with an SD card, and an external antenna. At the end of the ride, I want to put the card into my computer and save the tracks. Does this exist?