I have been waiting years for more seamless integration of VR, games, and exercise platforms. In the meantime I walk on the treadmill while browsing the web (at this moment, my treadmill is actually burnt out after years of overuse and we are scrambling to replace it =( ).
Unfortunately, VR goggles are prone to vertigo as there has generally been a little bit of delay in the visual feedback. So, I'm not sure it when/if it will be really safe to strap on a pair of VR goggles and walk on a normal treadmill.
However, I did notice a kickstarter for a "kat walk" VR platform in development:
https://www.kickstarter.com/projects...omotion-device. This is supposed to be safe because the walker is supported by a harness.
I've also seen a few "flying" platforms where you are basically prone (they look like fun, but probably not a ton of exercise without really working the leg muscles). Here's one:
http://mashable.com/2017/01/12/fitne.../#m.DlaHfkgaqx (I also saw one with actual flapping, but can't find it now).