I wonder if you could use the iPhone's hardware for real-time mud-mapping, building up scrollable representations of places as you go. You'd probably need the GPS to make it work properly, which would in turn mean it can't be used as easily for shopping centres, even though that's what triggered the idea for me in the first place. It would probably be too intrusive, as well, since you'd need to keep the phone held either up in front of you or panning around to get a good representation of the surroundings, rather than just passively gathering data as you go.
Mokalus of Borg
PS - I still think you could do location awareness with barcodes on the walls and image recognition.
PPS - That's if you could be bothered producing your own shopping centre navigation app.