Mark, I've been wondering about this for quite some time. I'm sure its possible, but not for me to attempt! When you have your dimmer wire hooked up, and turn your lights on, it switches the deck into "night" mode. What i would LOVE to see is when i move the dimmer control on my car's interior lights, for it to control the deck. I'm sure almost every car maker has different signals coming out of the dimmer line, but on earlier VW's the dimmer just controls the voltage of the line. Say for example with dimmer set to max the line is at 14v, and min the line is at around 2v.

Could you setup a config option that would enable the deck to control the display brightness based on how much voltage is coming out of the dimmer wire? Maybe also another setting for an offset for each volt lost or gained on the wire +/- 10%, or 15%, etc from the dimmer.