Are there any VR headsets for iPhone that feature positional tracking? There are VR headsets available for iPhone, like Google Cardboard, but Cardboard headsets only feature rotational tracking, not positional tracking like the Oculus Rift and the HTC. 

My question is, are there any VR headsets available for the iPhone which feature positional tracking?  And if so, do they feature outside-in tracking like the Oculus Rift and HTC Vive, or do they feature inside-out tracking like the products I list here?
So far the only VR headset I've found for the iPhone that does positional tracking is the Occipital Bridge.  It's $399 and it features inside-out positional tracking that doesn't require w computer.  It requires iPhone 6 or later running iOS 9 or later.  It ships in March but it's available for pre-order now.  I wasn't able to find any information on when exactly in Marxh it's shipping.

Other answers are welcome.