Rebtel is one of 65 companies chosen by VentureBeat to launch at the DEMO Spring 2010 event taking place this week. These companies do pay a fee to present, but our coverage of them remains objective.

By 2013, mobile VoIP applications will generate annual revenues of $32.2 billion, driven by more than 278 million registered users worldwide. (Sources: Gartner, Voipnews.com, In-stat and TCM.)

The Rebtel VoIP app for the Android OS is optimized for the Google Nexus One device. It brings simple, seamless and free international calling to the Nexus One and is the first app of its kind for the Android platform. The app gives its users free international calling with crystal-clear voice quality and without the need for a WiFi connection.

Alex Drewniak at Rebtel explained how Rebtel works: “We offer two different types of calling services. One is called Free Calls and one is called Direct Calls. Free Calls gives users the ability to make free international calls between the 50+ countries where the Rebtel service is available.

“Our premium feature is where we make our money. It’s not free, but offers savings of up to 90% in comparison to the international calling rates your regular carrier offers you. It’s significantly cheaper than Skype.”

1.8 cents per minute to India, to be exact. Skype rates to India run around 10 cents per minute.

Either way, you don’t need to download any additional software and you don’t need access to a WiFi connection to make the call.

Skype investors Index Ventures and Benchmark Capital put $20 million into Rebtel in the fall of 2006.

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