Re: inside out tracking - have you seen Bridge? It's a mobile, spatially aware headset for IOS. It uses an onboard Structure Sensor to power positionally tracked VR + high end MR. All on an iphone (no remote processing), and < $400 :)

We've been working on it in secret for a couple of years, and just launched it in December.

https://www.youtube.com/watch?v=Iys8yo0sjYg