In the case that a new image couldn't be mapped, the phone could still use its gyros to determine orientation and provide a route out along the mapping that it had made during ingress. A first-person-shooter-style "this way to the next waypoint" arrow, or something like that, could provide directional cues in low/no visibility situations.

It could also be networked with other devices, such that all of the routes mapped could be composited and help in the identification of alternative routes should one become blocked.