I have Vonage at home and the optional Vonage softphone add-in for my PC (with a 2nd phone #). Works like a charm when connected to an Internet connection. I've heard that you can just take you Vonage home box overseas and the phone service will work, but I haven't tried that yet.

As far as internet availability, for T-Mobile, check here: https://selfcare.hotspot.t-mobile.com/locat...balLocations.do. I haven't been in an airport in a long time where there was no wifi. Prices vary from place to place, and can often be free. Outside of the airport, I had a hard time finding Wi-Fi Internet in Japan though. You geek types can look at the first color chart on http://en.wikipedia.org/wiki/List_of_WLAN_channels to see why.

I'm a big time cell phone user, so both my Sprint and Verizon cell phones (with SIMs) have International plans. If a person's goal is to make and receive cheap calls locally, in a country that you'll visit often, it's not a bad plan to buy a pre-paid phone there in country. Cheaper to order a pizza on that local pre-paid phone than on your US phone. One can rent while there too, but I never have. If a person's goal is to receive calls from the states, with your family, friends, co-workers, etc calling you on a stateside phone #, then having a stateside phone with a SIM card works. Before I got my Blackberry Tour (Sprint doesn't use SIM in most of their phones), I had the option of either renting or purchasing a SIM-enabled phone from Sprint that would only be used overseas (As a non-revver that has the ability to go overseas often, I'd always buy rather than rent). I had to make sure that only one phone was on at a time, but when I landed, the new phone operated on the European networks with my stateside phone #. People were able to call me seamlessly from home and vice versa. I'm not sure if T-Mobile is a SIMless system too, especially on the pre-paid phones, but their sales reps should be able to help you with a solution.