@cbae: I made a suggestion on User Voice some time ago related to this, and I really wish they'd implement it. http://windowsphone.uservoice.com/forums/101801-feature-suggestions/suggestions/2285775-driving-car-mode
We have driving mode. Apps should be able to detect when the phone is in driving mode so that they can provide simpler, safer, interfaces. (Yes, you're correct, an appropriate interface is no less distracting or dangerous than turning on your radio, adjusting the temperature, turning on your wipers, etc. So @spivonious is off base here.) Even the start screen should be customizable when in driving mode. For Xbox music all of the interface for selecting songs could be removed, forcing you to use voice control, which is safer. The display would just be the cover art with swipe gestures for pause/play and next/previous tracks. Audible has a nice "button free" interface (well, nice other than it's ugly) that would work great for its Driving Mode Display.
Like I said in my User Voice response, we shouldn't be limited to just Driving Mode either. Allow other modes to be defined as well, so we can limit the apps available, change the volume settings, turn on auto replies, etc. for each mode. Then we could have a Work mode, a Church mode, a Movie mode, etc. You should be able to manually switch to any mode via the new Action Center, and you should be able to define events (time of day, logging on to specific WiFi or Bluetooth devices, tapping certain NFC tags, etc.) that will automatically switch you to a specified mode. This sort of personalization would put WP ahead of other platforms (which are currently ahead because they can already do a good portion of this).