Mark; don't have a problem with either Zumo or my current TomTom or whatever the system is in our car. Never used route tracking so not sure about that. I remove the GPS from the mount for lunch and coffee stops, busy petrol stations and overnight on long continental trips. All the units I've had just light up again and continue with the planned route when switching the ignition on (they also adjust the ETA, average speed etc). Maybe I'm missing your point, but I have an aversion to lengths of 'hot' wires.
Steve, I've added bullet connectors to the ends and plugged in to the "Accessory" ports.
I've also replaced the 5amp fuse in the fuse box with the 3amp fuse that came with the Garmin.