navmo service is unique, however, in that it's a straight JAVA WML based app, so for many phones nothing but a page load is required ?? best guess is that this is done on the operators end by triangulating the location of the user from tower to tower, but navmo's being a bit mysterious about such details.
http://cellphones.engadget.com/entry/1234000290029043/
Reporting by Costas Stephanides (Editor)
Checking this - navmo's GPS-less nav pilot launch in LondonTweet & Track