It's called Omni, and like the Oculus Rift, it's still under development. But once unleashed, there's virtually no limit to how the two devices could be used together.
Omni's creators describe it as “a natural motion interface for virtual reality applications," and that it will be the first treadmill of its kind to be affordable for household consumers.
From their website:
Applications of omni-directional movement in virtual reality stretch far beyond gaming: training and simulation, fitness and exercising, virtual tourism, virtual tradeshows and events, virtual meet-ups and multi-person adventures, virtual workplaces, virtual museums, physical therapy, VR architecture, VR concerts, etc. The possibilities are limitless. Virtual reality is the future.
Virtuix is currently preparing a Kickstarter campaign to help launch the Omni.