thanks for the pointer. I had a look at their offering and really like their approach of streaming NMEA-formatted data. The limiting factor for me here is the indoor limitation and the limited reach of the sensors.
I also envision a seamless fusion, an EKF blending of "fake-GPS" (coming from beacons) and "real" GPS.
I have not quite thought this all through, but at first glance I should think for this to work - for going from "inside" to "outside" - the beacon position (network) would need to be precisely calibrated. So basically one would need to establish the GPS coordinates of a secondary positioning network (which is setup in a GPS-denied environment).
But maybe there's a smarter way to keep positioning absolutely accurate and repeatable - in both environments?
Would be great to keep up the discussion to find a real-world solution.