Uhm, not sure if it will be of great help, but I guess it wouldn't hurt. Some folks over at dd-wrt (it's a third-party linux-based firmware for home routers) wrote a script which does exactly this -- it picks up the open wifi AP with the strongest signal, checks if it connects to internet (some open AP require the login/pass to get the actual internet) and it cycles to the nest strongest signal on failure.
Given that that script works on linux, I'm guessing it could be of help. I'd post a link to the forum thread, but not sure if it's welcomed on this forum.