http/https redirection and captive portals

[mor1]

two things

1. captive portals. worth trying to implement i think, given doesn't seem too hard. http://en.wikipedia.org/wiki/Captive_portal for background, http://stackoverflow.com/questions/3615147/how-to-create-wifi-popup-login-page for some apparently simple instructions.
2. _http/https redirection. related to the above -- https redirection as well would be nice, but isn't a requirement by any means if it's hard. a self-signed cert (the same one on every router) would be fine -- some browsers don't pop an error, and many users (probably -- i think there's evidence for this) just click "ok" anyway. even if we bought one, we shouldn't need a new one for every router (i think -- just gen a different one under the same subdomain each time?), and unless we did DNS redirection i'd still expect a browser to pop errors as the domain requested wouldn't be within the subdomain covered by the cert. (though my in-depth knowledge of https/tls is fairly limited so i may have that wrong.)