In-car navigation might just get a little more interactive if the Virtual Cable can get to market. The concept is to provide a 3D windshield display that projects a trolley car like cable above your desired path. You have to watch the video to get a real feel for it:
Demo video

I would have written it off as a nice concept without any reality behind it. However they provide ample information on how the projection system works and how it would be installed and implemented into a car. After you watch this Explanitory Video you really get the feeling that this is possible and should be in your car right now.

I think it will take a while to get something like this tested and approved from a safety standpoint, but getting it integrated with current GPS systems will be a bit more challenging. It just seems like combining digital navigation with real world landscapes could be a daunting task.