Make cheap VoIP calls using a cellphone

They're rather skimpy with the details, but i2 Telecom says they're coming out with a box called the InternetTalker MG-3 that'll let anyone make cheap Voice over IP phone calls using their cellphone. We're guessing it must be some sort of Vonage-like setup that requires a broadband connection (trying to piggyback on a cellphones Internet connection would be a really bad idea for a lot of reasons), but if that's the case, isn't it usually easier to just hook up one of those boxes to a regular telephone? Any advantage to using a cellphone over a regular phone is eliminated if you have to stay at phone use it anyway.