Here is an invention that makes me go "Now, why didn't I think of that?". A heads up GPS navigation system for cars.
It is called the Virtual Cable. The driver sees the Virtual Cable - a line representing his path - projected on to the windshield. It looks like its a suspended cable - hence the name "Virtual Cable".
According to the inventor's website "The image is in true 3D and appears to be a natural part of the landscape. The driver uses only peripheral vision to follow the Virtual Cable™."
More about the technology: http://www.mvs.net/technology.html
The device is only a prototype right now and from the looks of the site - the inventor is trying to line up funding for taking this device to production.
Will be cool to see how the finished product looks and how much more information is displayed on the wind-shield.