Well, the language-preference stuff works great; there's an article about that somewhere here on phpbuilder. But if you intend to base it on domain name, good luck! Not only will you have to turn on dns resolution, slowing your whole server down, but what will you do if an ip address doesn't resolve to any domain name at all?
I guess if we know the purpose of this, we could give better advice. If you're just trying to be helpful to the folks from the special country, go ahead--the worst that could happen is you aren't as helpful as you wanted for those who fail the "what country are you in" test and they get the same page as everybody else. But if you're trying to restrict access in this way--all I can say is to repeat Good Luck! but don't trust your system at all.
