Laptop in back panier connects via serial port to a GPS unit mounted on handlebar. A Lucent range extender gaffer taped to backrack leads back to wireless card in laptop. Headphones lead out of laptop to head!
Run a quick bash script on linux or netstumbler on windows - and RIDE!
Mapped results of the war pedalling will be up on free2air RSN. In the meantime, London raw scan data from over 40 wireless networks scanned in one afternoon around London, some of which should definitely know better than to put them up with default configurations.
Call to Arms! Email War Peddlaz and join them in their ongoing campaign rides.