We made an educational game that allows the user to drive a car in a 3D space while learning and interacting with animals. When you approach an animal, your score goes up and you get to read a little more scientific information about them. This technology is most applicable to the education field for better engagement of small kids to learning.
Our greatest challenge was attempting to connect the Oculus Rift to Unity. After trying to do this for 10 hours, we gave it up and chose to make it a Desktop application.