[dentheman]

Keep in mind that if you wire this to the battery whatever is plugged in will continue to draw current even with the ignition off. Correct me if I'm wrong, but I think a gps turned off would continue to pull a very small amount of current for the clock and perhaps some other functions.

Maybe that's why I previously mentioned a relay.

I am curious to see how you mount this, since it doesn't appear to have lock nuts on the barrel.