A company called Occipital launched a room-scale motion tracker for iOS and Android. This developers kit uses Structure Sensor which is a product Occipital already sells as a 3D scanning and Augmented Reality devices that you can mount on an iPad combined with some sort of camera lens.
VR users will be able to walk in a room tracked by the Dev kit while immersed in Virtual Reality. You won't bash into stuff thanks to its depth-sensing capabilities.
The dev kit costs 499$ and is compatible with iPhone 6 and 6S (and probably iPhone 7 and 7S).
When you buy the dev kit you get access to a "Bridge Engine" which includes 6-DoF positional tracking for VR, but not yet in the public Structure SDK
The VR Dev Kit includes all you need to create and experience mobile augmented reality and virtual reality applications with large-scale 6-DoF positional tracking. Compatible with the Bridge Engine for mixed reality and Unity for iOS. The VR Dev Kit includes a virtual reality HMD with custom 3D printed faceplate, a custom 3D printed case for iPhone 6 and iPhone 6S, and a Structure Sensor. The website states that the dev kit is available in limited quantities for qualified developers.
Combining the dev kit with your iPhone you get HTC Vive capabilities! Just look at the video bellow.
Let's hope Occipital is working hard on releasing the consumer version.
For now, if you are an Apple user and you are not willing to spend 500 bucks on a 3D printed developers kit, you'll have to continue to use a simple VR headset or Google Cardboard.