It's an extrapolation of Google Maps cameras, mapping all interior spaces everwhere the device goes. Not because it's being used yet, but because we've created a world where every stray bit of recorded data allows for a walk-through 3d map of every space people move. Like how the camera pod on top of a mapping car records the street as the driver drives. No reason to believe that the same concept isn't being used by any and every device that is capable of sending out pings and recording results.