Maybe check out www.roadpost.com. I've used them in the past for travel in Africa. It can be a bit pricey depending on whether you go with an int'l cell phone vs. a sat phone. Now I just use a SonyEricsson phone through Cingular that is a quad channel phone, which means I can use it in pretty much any country. I'll just have to pay a roaming charge wherever I am.

i don’t clear if there is company doing rent cell business. But i can give u another choice, buy a cheap quad phone.
they are made for this purpose mainly, i think