I was planning on making a stripped skin that would be designed for my purposes, but wouldn't be that hard to modify for your purposes.
I use winamp for music, iGuidance 3.0 for nav (upgrading soon to 4), and will focus on music and gps. I think for you, the hard part would be how you enter addresses, etc. or anything that needs text entry.
I was playing with the idea of something like this:
When you rotate the knob, each icon grows a little and glows to let you know which one you are on. The left wall and the right wall are hidden buttons for me that offers further options for that specific menu item. (This would be the audio screen, so if I press the left wall or you press left on the knob, it will load the audio browser screen, etc.) The ceiling is a button to bring up the menu from any screen.
Once I learn flash a little better, I want to animate the floating screen (which will be changed to a pic of a real flat screen for realism) to enter and exit the room.
What do you think of this so far?