Last year I did my master thesis computer science about a virtual reality multiplayer game. The idea was to play a game on the oculus rift while walking around in real life and move at the same time also in the virtual world. The game was created in the jMonkeyEngine. We managed to come up with a prototype and had some fun with it. If you are interested you can read the paper version (6 pages) that I presented on a conference in Mexico or the full thesis.
We also posted a videoclip on youtube where we explain the concept and show a short demo.