This is functionally equivalent to Google's Tango, MS' Hololens, and whatever Intel is using for their AR/MR HMD. Not to say it's not faster, more accurate, or doesn't do more. But, the core functionality is the same.
BTW, it's no coincidence they didn't demo this in a room with blank, white walls. I'm sure the bookshelf was there to aid tracking.
problematiq :
One problem I could forsee, How do you tell the device where position x-0 y-0 z-0 is? You can track position by movement, but can you track/reset your starting position?
The origin is arbitrary. What's important is that the device maintains a stable coordinate frame. If you want to map a different point as the origin, that's just a simple transform you can apply to the pose determined by their SLAM system.
Think of it like this: if you want to tell the app "treat this as the home position", it can take the pose (position + orientation) and simply offset all future pose readings by that amount.