VoIP services over Wi-Fi enabled cellphones available from Gorilla Mobile Jajah and iCall. Some of these services claim you can save up to 98% on international calls.
By 2011 the number of mobile VoIP users around the world could increase to 100 million from 7 million in 2007, according to consulting firm ON World in San Diego, reports Business Week. ON World also estimates that in 2011, mobile VoIP voice services could generate $33.7 billion, up from $516 million in 2006.
T-Mobile in order to cap Wi-Fi VoIP have rigged their handsets so VoIP calls made via Wi-Fi hotspots are charged against the subscribers’ wireless minutes unless they pary for an for additional $10 plan.