Startup VoIP provider DeFi makes big claims, but delivers worldwide calling from a smartphone for $40 or $50 per month: DeFi has a very stripped down business model designed to appeal to a specific, but large class of traveler. They make software that's currently available for Nokia S60 phones (E and N series), and later this year for the iPhone, that acts as a kind of VoIP shunt for calling behavior. When you place a call, the software determines whether you're on a Wi-Fi network, and routes the call out that way; if not, it goes to cell. It also routes inbound calls, and can ring your cell phone's number if you're not on a Wi-Fi network and your inbound DeFi number gets a call.
For $40 or $50 per month (1 or 3 inbound phone numbers, respectively, in any of about 30 countries), you get 3,000 minutes (they call it "unlimited") of calling to and from 75 countries. This includes cell lines in Europe, typically a huge extra for most VoIP plans. DeFi said they signed deals directly with carriers, which they say most VoIP providers have not.
Wi-Fi access works at what they say is "1 million" hotspots, but is really Fon plus several tens of thousands of typical hotel, café, and airport venues. Wi-Fi fees are included for VoIP and data in the monthly subscription. DeFi uses Devicescape behind the scenes to handle no-entry authentication to their Wi-Fi footprint.
The integration is the key point DeFi makes about their product, and may be a stumbling block for an iPhone application. The head of DeFi told me that the company wants their service to require no behavioral changes for customers. Of course, users still have to make sure when they're in areas in which a cell call would be expensive that they don't accidentally wander away from a Wi-Fi hotspot. And Apple doesn't currently allow the kind of integration that would be required for call handling and interception, although DeFi said it's having no problems in its development work.