I've never used this myself, but there is a VoIP service called "Follow Me" (different providers have different names...) which allows a single phone number to connect and ring across multiple lines and locations like cell phones and Wi-Fi connected laptops. “Follow Me” will allow you to travel without missing calls and erases the need for separate phone bills or long distance lines. Another innovative option called Outlook Integration allows calls to be sent from Outlook email boxes. For the most part, VoIP options give you a lot of shortcuts. Perhaps the best part of traveling with VoIP (especially worldwide) is saving on long distance calls - they're all technically free because you're only paying for internet service. But since there aren't that many VoIP phone options - like actual phones for sale - out there, you may NEED something like "follow me" to use it globally.

Source: http://www.ResourceNation.com