I agree it's a bad idea to have touch devices within an arms length of a drivers seat, even if the device can be interacted with also via voice and physical buttons.

It would would be simple to not allow touch interaction while driving. So before you start and if you pull over you can text/call/setup navigation which is easy to do on the touch screen and hard to do with a few buttons.

Once moving the touch screen should dumb down to stupid mode with only one valid interaction: hitting the screen hard a few times should silence the navigation voice (a feature I have found missing in most current models).