This would be neat, especially if it doesn't count minutes, but can we really expect AT&T to set up a VOIP system for iPhone users? Especially when they're starting to introduce femtocell stations for home use that carry calls over VOIP.
I don't see as femtocells are any different than WiFi, just on a different radio frequency. Both femtocells and WiFi serve the same purpose, to connect to phones in a local setting and route traffic through a wired internet connection (aka VoIP). Femotocells are simply available to phones that do not have WiFi.