Something I was thinking recently is using a lighthouse positioning system from Valve for indoor positioning. They have permissive licensing terms and the tech looks very promising:
UWB is our present solution, its already easily in the 10cm accuracy in LOS scenario, it also enables complex indoor space with different connected rooms you want to cover, and you could cover easily 30m between each beacons.
We are discussing the option to integrate the optical flow directly into the ArduBee base. If you have suggestions, your contribution is highly appreciated.
