As many learn the hard way, traveling overseas is one big wild card when it comes to cell-phone service. Will your cool new phone work in Europe? Japan? Thailand? Doubtful, but it's a good bet National Geographic's Talk Abroad phone will, since that's exactly what it's designed to do. You can rent this bare-bones cell, starting at $69 a single week, which also gets you 30 outgoing minutes of talk time in 50 countries (including Herzegovina!) and a U.K. phone number that people can reach you at.
If you love the idea of an ultrasimple cell phone for your trips abroad, you can buy NG's phone for $199 or get a SIM card for $79, putting more minutes on as you go (you still get the initial 30 outgoing minutes with purchase). Buying this phone seems pretty silly, though Cellular Abroad (the provider) does promise "inexpensive rates and great coverage," so if you travel a lot, it might be worth a look to compare with whatever your wireless company charges. But for short hops into the wild where I want to be sure to stay connected, I could see going for a rental.