WiGLE is a massive user contributed database of WiFi access points and GPS coordinates. IronGeek decided to take that data and parse it into a KML file that Google Earth can understand. It uses cached data from WiGLE’s Java interface, JiGLE. Reader [bird603568] has been playing around with the script so that it will indicate the quality of service in addition to IronGeek’s showing whether or not WEP is being used. Visit his site if your interested the QOS feature.
[UPDATE: corrected based on bird603568's comments]