New mobile operator Truphone has announced a beta application to provide free calls to Wi-Fi enabled mobile phones.
Truphone also hopes to launch a version compatible with Microsoft Windows Mobile in the near future.
Worldwide calls between Truphone-connected handsets are free. As a launch offer to the end of the year, US users will get free calls within the US and to Canada, and UK users will be able to call some two billion landlines in major countries for free.
All other Truphone calls from the user's mobile will be charged at " characteristically low" VoIP rates.
Customers can set up their account by sending an SMS with the word 'TRU' to the appropriate number for their county: 60030 in the UK and +44 7624 000 000 in the US.
The software integrates with the phone's existing address book. Once set up to use a Wi-Fi hotspot, the handset connects automatically next time the phone is in range.
Truphone chief executive James Tagg said: "Truphone is the natural evolution of VoIP. First people talked to a PC, then they were tied to fixed-line handsets and now Truphone takes VoIP mobile. Free calling has arrived on mass-market handsets."
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