Not content with providing TV on mobile phone, Rok has taken a large step into the VoIP market with Rok Viper, which enables users to make calls using VoIP on their mobile phones.

By installing Rok Viper software on a mobile phone, users can call other mobiles for free using VoIP – but there is a catch.

The service works rather innovatively by using Bluetooth technology to connect Bluetooth-enabled handsets to a user’s Bluetooth-supporting PC, but this means that you must have the computer on in order to use the service.

Like Skype and other VoIP companies, the service does require that the person you call also has Rok Viper installed on their phone.

At the moment, the software is only compatible with six Nokia mobiles, but Rok plans to add support for more than a hundred before the end of the year.

Once Viper is installed, it shows you a list of Viper contacts on your mobile, and who is online and available for calls.

Once the service takes off, it will save people money on tradition mobile calling, and let them ring people anywhere in the world for free over their mobiles.

For more, visit the Rok Viper’s