I will try to make a video of this soon but the process is so simple, I thought I'd just post it first.
I love the droid Multimedia Station at home because it turns my droid into an alarm clock when I dock my droid on my nightstand. The magnet inside the dock is what triggers the droid to change its display.
Unfortunately, there is no "dock" for the car. They make a mount with a magnet which puts the car in nav-mode but the mount does not have a built-in charger.
With some experiments with a refrigerator magnet, I found out that it's not the placement of the magnet which triggers droid's mood, it's the polarity. Just hold a magnet half-way between the M-logo and the right edge of the bat-cover and the droid will go into nav mode or dock mode. Whatever it is, just flip the magnet over and the mode will flip as well.
So, if I wanted to modify the droid multimedia station so that I could use it in my car in nav mode ... all I needed to do was flip the magnet.
To do this, the only tools needed are (1) a small eyeglasses screwdriver and (2) a sharpie.
(a) On the dock itself, there is 1-inch T-shaped piece of plastic sticking straight up which serves as the backdrop for your docked droid. On the back of this "T", is a grey sticky cover. Simply slide the small eyeglass screwdriver along the top edge of this sticky to peel it off. Set this aside as you'll need it later.
(b) Under the sticky, you'll see a small round magnet in the upper right corner. Take your sharpie and put a dot on the magnet to mark it as the "negative" side.
(c) Next, slide the small eyeglass screwdriver under the top-right portion of this magnet to pry it out slowly ... don't let it fall on the floor cause it can roll away and get lost.
(d) Now that the magnet is out, simply put it back in with the marked dot side down.
(e) Finally, reapply the grey sticky cover and you're all set.