Thanks to the folks at fring, you can now use a jailbreaked iPhone or iPod touch—one opened up to unofficial native software—to place and receive phone calls and chat over a Wi-Fi connection. AT&T, which makes much of its money off the iPhone through voice and text-service revenue, isn't going to be happy about this development.

With the software, currently in pre-release, users can interact with other fring users, get VoIP phone service through Skype-based and IM-style live chat with others through MSN, Google Talk, ICQ, Twitter, Yahoo! & AIM. The service works no matter if their buddies are on a mobile phone or PC at the other end of the connection.

During login, fring automatically creates a single, integrated contact list, combining contacts from all of the users’ selected internet communities. Because fring is always on, it offers real-time, PC-style “presence” indicators that continually display whether contacts are online,

The company developed the iPhone fring application with the Holon Institute of Technology academic research labs in Israel. It is available here.

Fring users can be found in over 180 countries, with the service experiencing an average growth rate of about 100,000 new users a month. It is free and there are no subscription costs.

In addition to the iPhone, fring is available for Symbian (Nokia S60 and Sony Ericsson UIQ) and windows Mobile smartphones.