If the goal of this new wave of VR gaming accessories is to allow for truly immersive gameplay, we're gonna need to use our entire bodies. The PrioVR bodysuit (now on Kickstarter) allows you to gain real-time, full-body control over an in-game character. You could conceivably even ditch the Omni treadmill and still be fully immersed in the game, at least until you ran into a wall.
What's truly impressive about the PrioVR suit is that it seems to have solved the nausea-inducing lag issues that still plague the Oculus Rift itself. If this is true, the entire VR gaming community needs to take a step back and check out how the PrioVR guys are getting the job done. After all, YEI technology (the company behind the PrioVR suit) has been in the business of manufacturing real-time inertial sensors since way back in 1999. Their tech is even used in medical and defense sectors.