Jim Parsons at Mexens technology has recently released AlwaysOnGPS - which successfully blends GPS positioning and Wi-Fi positioning together into one accurate system.
When GPS signals are available, the software uses them to construct a map of the Wi-Fi "landscape" around the receiving device. When GPS signals are lost or dropped (which occurs frequently with client vehicles, assets and cargo in big cities, indoors, etc.) this WiFI map
provides accurate geo-positioning information to maintain an accurate track and location determination -- all the time and in every situation.
In a recent email, Jim said that "So far, all our tests and real world applications have produced amazing results . AlwaysOnGPS has proven itself to be an indispensable companion for customers who simply can't afford to be without GPS signals when entering and operating within big cities or large buildings (warehouses, distribution centers, etc)."
It seems that mobility is now about never being lost again!
You can find Jim and more details on his product at: www.AlwaysOnGPS.com