WIFI Locator is a small utility that runs in the background, and monitor the activity of wireless networks around you.
For each detected network
WIFi Locator offers the possibility of giving the exact location system that quickly determines device location with 10 to 20 meter accuracy. To quickly and reliably arrive at accurate location results, the Core Engine collect raw data from Wi-Fi access points. Cell tower triangulation provides generalized location results with only 200 – 1000 meter accuracy.
Google have a database of Wifi access point locations created by driving cars around. This database, in combination with the nearby Wifi details, is used to determine your location. in this way are able to give you your location using Wi-Fi towers only without the use a real device GPS very surprising.