The British are bringing VoIP to your iPhone.

In a demonstration at this year’s DEMOfall07, British VoIP provider Truphone showed conventioneers how to use the iPhone’s built-in Wi-Fi capability to make calls over Truphone’s VoIP network. Truphone representatives demonstrated how a call can be initiated from a handset and then routed to Truphone’s server via Wi-Fi.

Truphone spokesman Tim Donnelly Smith emphasized that the event at DEMOfall07 was only a demonstration and was not intended to be a commercial launch. He also said that the program is a native application that is installed through third-party application installers, and does not require cracking the iPhone’s SIM card. This is significant in the wake of Apple’s declaration earlier this week that “many of the unauthorized iPhone unlocking programs available on the Internet” could render the device “permanently inoperable when a future Apple-supplied iPhone software update is installed.” Several iPhone users have reported that installing Apple’s iPhone 1.1.1 update rendered their unlocked iPhones useless.

“This program doesn’t do anything that Steve Jobs says not to do,” said Smith. “Apple is fairly neutral on third-party applications and they won’t deliberately try to break them.”

In addition to its demonstration of iPhone over VoIP, Truphone demonstrated an application that allows people to call each other through the social networking site Facebook. Essentially, the application would let Facebook users embed a “call me” button into their Facebook profiles that would let friends call them without revealing their actual number over the Internet.

Smith said that the application would allow Facebook users to contact friends who use both VoIP and PSTN networks. He also said that this application is still in development and is not nearly as far along as the iPhone VoIP application.

Truphone bills itself as a “mobile operator for the Internet era” that offers “free mobile calls to other Truphone users or very cheap calls to anyone else.” Its services work anyplace where there’s Wi-Fi or 3G, and it is available for use on various Nokia phones.