When I've headed out somewhere new with friends and ended up in a strange place at 1am, Google Maps public transit directions are my lifeline. If I drove I could just head in the rough direction or use a streetmap, though transit maps aren't usually complete with all routes and times. There is nothing worse than standing at a bus stop for an hour hoping a bus will come, and that bus will take you home. Train stations are alright if the trains are still running, but usually I need to rely on a late night, barely functioning bus network.
I would love an e-paper/ink phone that did maps, texts, calls, photos and nothing else.