The American Printing House for the Blind’s Nearby Explorer app is a GPS app designed for users who are blind. It has recently begun developing support for indoor location and navigation, using indoor data from OpenStreetMap and Bluetooth beacons for location (mapped using indoormark=beacon).
Indoor Navigation: The Next Frontier (APH News July 2017)
Nearby Explorer with Indoor Explorer (YouTube)
To this end, a few local buildings have been tagged using Simple Indoor Tagging: APH, the Crescent Hill Public Library, and LouieLab (a civic innovation hub and co-working space).