Thinking of adding location to your mobile application? Need a cellid based solution like Google maps cellid location? The problem is that you have to somehow generate (over time) a database of cellids vs GPS positions.
Navizon solves this problem by providing a collaborative database of not only cellids but also WiFi access points. What makes Navizon especially useful to developers are the iPhone, Windows Mobile, Symbian (S60) SDKs that allow you to plug Navizon software based location into your application. (Java ME is coming soon).
If you take a look at the white paper, it explains how Navizon works. It triangulates WiFi access points and uses cell signal strength to interpolate positions.
Navizon also provides some end-user tools to map your position, map your buddies or provide email alerts when a phone enters a particular area. You can even get paid via Paypal for contributing GPS fixes to the database. However, their points system vs payout is particularly low and you are not going to get rich very quickly.