Sound in your car is really not an option.
If you have tons of money or are a big ol' computer geek with tons of geeky gear, then you could stick a cheap computer in your trunk with a wireless card and use the ppod as your remote. Win2000AdvServer, Citrix, a big hard drive, a DVD drive, GPS unit, power converter, and sound input. . .you'd be set! and unfortunately very broke.
You'd think there would something really cool to do with it in your car. If you don't already have wireless cards and all that software than you'd almost be better off selling the ppod and buying a cool touch screen display for your car (and using a regular cpu).
That way you could do a lot more than mp3s and gps, for a lot less. But, than you don't have the panasonic.
who knows. who knew?