I don't have one yet, but I think I'm going to pick up a
Pro Fit VSM G3. I like this one because it uses a vehicle-specific mount with a ball head that can fit any device-specific holder. I'm not sure how you'd get power to it cleanly, but I'm also not sure I need power.
Here is another mount option. This one isn't as attractive, but there's a wider range of holder's available and some of them have integrated power, like
this one. The location of this mount makes power cables a bit easier to deal with, too.