The current race ongoing is the competition to get VoIP onto mobile phones. The latest company to join the fray is iSkoot which says that using their software, any dual mode phone that downloads the program will instantly become a VoIP phone as well. The software works using wifi, 3G/GPRS data and GSM/CDMA network connections.
Dual mode phones are units that support both wifi and GSM/CDMA networks. The Nokia E series is an example of compatible handsets More phones are sure to follow.