Not iPhone, but related...
It's been said that Google does the same thing with their Android devices (except it sends its data back to "home base" more often than iPhone/Apple). Their street view cars used to collect wifi data also, until it was found they were collecting more than just BSSID's. Anyway, so Google's giant database of BSSID's is searchable and Samy Kamkar made a nice little app to search it by BSSID, which will then map it along with all the data.
http://samy.pl/androidmap/