I would drop this idea entirely. Connecting to a wireless access point without the permission of the owner is treading on thin legal ice. People have been arrested in their cars outside of establishments using the WIFI.

Secondly I really am hesitant to connect my device to "strange" access points. To many security issues there IMHO.

There is a program where people sign up to share their wifi with other members of a community I forget the name but that would be the best legal option.