Hey!
I have seen that recently people have been wondering about an app called 'MineChat' which from what I can tell, allows them to see the server's chat without being logged in. I thought that maybe a way to resolve this is to get an IRC plugin such as the one I have linked below, as this will allow the server to connect up to an IRC channel which it could create, and then if people wanted to log into the server chat, all they would have to do is log into the IRC, which there are many ways of connecting to via apps or on the web.
I just thought I would bring this up as it might be useful and a nice thing to consider! Again if you need any help testing, I would be happy to help.
Luis
IRC Plugin (There are many but this is one I use):
http://dev.bukkit.org/server-mods/craftirc/IRC Service (Again, many but this one is quite popular):
http://www.esper.net