Actually, the navigation unit uses the older style audio/power connector for the sound/power but adds a connector that gets more info from the car, including, yes, the emergency/parking brake grounding signal. I have done a write-up on my experience defeating the while moving DVD / Navigation lock-out and you can find it here:
So the nav uses this connector for sound:
And the one pictured below for other vehicle info.
Also, here is a pic of the Navigation connector: