What I want to be able to do is within a window of time (eg a couple of hours) after I leave the car, is to still be able to access the empeg remotely - eg to upload new music that I just bought - from my flat. The empeg unit partially has this support through the "power off timeout" setting - however I also need to provide power to the wireless/ethernet convertor for the same duration of time. I could implement my own timer circuit triggered by the ignition being switched off and holding the power to the convertor for a fixed period of time - but it'd be neater to link it to the empeg's built in timer. The signal on the tuner connector I mentioned before seems to change state exactly when I need it to.

S