Truphone to Demonstrate First VoIP-over-WiFi Call on Apple’s iPhone
According to a company called Truphone, they have unlocked the secret of IP telephony on the iPhone, and demonstrated said ability today at DEMOfall 07 in San Diego. Executing commands via the Terminal (i.e., on a phone which had been Jailbreak-ed), Truphone CEO James Tagg was able to call another mobile phone using only an IP connection — all without breaking the SIM lock.

According to the company, the software is still in beta, but they soon plan to have a version which will simplify activation, and allow seamless switching between WiFi and SIM use. Clearly, an exciting development for iPhone users, but a cringe-inducing situation for AT&T.
Source: TechAmok