I've not used it myself, but check out riiing (three i's): http://www.riiing.com/

See also http://www.prepaidgsm.net/en/int/riiing.html and discussions in their international forum

And also in this thread (high noise content, just search for riiing) on Fodors:
http://www.fodors.com/forums/threads...2&tid=34579048