Valve is heavily involved with HTC on their Vive VR headset scheduled for this year. They created an Aperture Science demo to demonstrate a VR environment in which you could physically walk around in a room with and interact with! They've begun showing it off more and here are some videos, one with commentary and one without that takes you through the demo from beginning to end! Very cool stuff! Hopefully someday we all can get a chance to try it out!