You really want a carrier-phase-tracking L1+L2 receiver on each end for that sort of usage which isn't inexpensive (yet). The beacons also could be adopted by

You really want a carrier-phase-tracking L1+L2 receiver on each end for that sort of usage which isn't inexpensive (yet). The beacons also could be adopted by future indoor projects of theirs... that would be really nice. My roomba gets lost easily when it starts getting dark out.