50x more accurate geolocation using contact page info

Have a look at Skyhook, cited by developers as an upgrade to Google's location service built into Android, and as the location service in original iPhones:

http://www.skyhookwireless.com/

In general, it's considered superior to Google's service. Citation:

In comparing the two systems, Fruzzetti notes that Google’s technology can be off by as much .2 miles, whereas Skyhook’s technology has attracted manufacturers and developers like Motorola, Gowalla and Peekboo with “accuracy within 10 to 20 meters.”

http://bostinnovation.com/2010/09/28/skyhook-v-google-iath-4...