  We introduce two iOS apps that have been designed to support wayfinding and
backtracking for blind travelers navigating in indoor building environments.
Wayfinding involves determining and following a route through the building's
corridors to reach a destination, and assumes that the app has access to the
floor plan of the building. Backtracking one's route, on the other hand,
requires no map knowledge. Our apps only use the inertial and magnetic sensors
of the smartphone, and thus require no infrastructure modification (e.g.,
installation and support of BLE beacons). Unlike systems that use the phone's
camera, users of our apps can conveniently keep their phone tucked inside a
pocket, while interacting with the apps using a smartwatch. Routing directions
are given via speech. Both apps were tested in a user study with seven blind
participants, who used them while navigating a campus building.
