Vivox, a voice app maker, is partnering with mobile carrier T-Mobile today to turn Facebook into a phone company. Together, they have created the Bobsled by T-Mobile app that lets Facebook users call each other for free with a single click on a PC.

The recipient of the call doesn’t even have to have the Bobsled app installed in order to receive the call. If it takes off among Facebook’s 600 million users, the app could turn Facebook into one of the world’s biggest phone companies.

The app is powered by Vivox’s VoiceEverywhere Service. It allows a Facebook user to make a voice-over-internet-protocol (VOIP) call to another Facebook user through the social network’s chat window. That’s pretty simple, and the user only needs a voice headset on a computer to make it happen. No application download is necessary. Users can record and post voice messages to their friends’ Facebook walls. Users can also call friends on Macs, PlayStation 3s, iOS devices (iPhone), and Android mobile devices.

Vivox created its first voice app for Facebook
in the fall of 2009. That was a group-chat app. The company later replaced that with Vring, which was inside a Facebook app. Now Vring is being re-branded as Bobsled. The Bobsled app has more marketing clout behind it with T-Mobile as a backer. And this app is natively integrated into Facebook’s chat system. When you pull up a Facebook chat window, you can see a phone icon. If you click on that, you can call your friend. It’s instantaneous.

Right now, the Bobsled app is built into the web version of Facebook only. Over time, T-Mobile plans to add video chat and the ability to place internet calls to mobile and landline U.S. numbers. And it will offer internet calling apps on smartphones and tablets across mobile platforms, regardless of the carrier that powers those platforms.

Vivox serves more than 50 million users worldwide and delivers more than 3 billion voice minutes per month through its integration into social apps, online and console games, and virtual worlds. Vivox, based in Natick, Mass., was founded in 2005 and has 38 employees. Rivals include Skype, Ventrilo, and Teamspeak. Vivox has raised $22.6 million to date from Benchmark Capital Canaan Partners, Grandbanks, IDG and Peacock Equity.

This April 25-26, VentureBeat is hosting its inaugural VentureBeat Mobile Summit, where we’ll debate the five key business and policy challenges facing the mobile industry today. Participants will develop concrete, actionable solutions that will shape the future of the mobile industry. The invitation-only event, located at the scenic and relaxing Cavallo Point Resort in Sausalito, Calif., is limited to 180 mobile executives, investors and policymakers.

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