I bought an indiegogo project called the Airdock and it arrived the other day. It uses magnets and a sticky foam to hold the phone and includes a Qi charger to charge wirelessly. If you position the phone right, it will both charge and launch car mode (from the magnet in the dock.)
It's a nice solution for the Maxx. I've held the thing with my phone on it upside down and shook it pretty hard and it still stays on the dock.
Air Dock
Pricey (though the indiegogo price was less), but I think really worth it, with Qi charging so you don't have to fumble with plugging in the phone. (I could never get the Griffin dock to charge my phone.)