http://www.fandome.com/video/107610/The-Mystery-of-the-Yellow-Line/
A subset of virtual reality is augmented reality. In augmented reality, computer generated graphics overlay images of the real world.
Here is a video explaining how the first-down line on football broadcasts actually works. This is probably the example of augmented reality that most people are familiar with.
This topic has fascinated me for sometime now. I have an extensive primer of it right now detailing some the the great applications for the future. Great post keep it up!