Ever since I got my new mobile (HTC Hero) which has both GPS and WiFi, I've been wardriving; simply run a program and it does all the dirty work of scanning for wireless networks and attaching the geographical location of these access points (APs).
The program I use is wardrive. It's written by Raffaele Ragni and is freely available in Android's market.
The purpose of this project is to collect statistics and show a map of open and secured access points along with other things.
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If you'd like to contribute to this project, email me: mbhkewl TheAtSign gmail Dot com.