Truphone is a free piece of software that enables Wi-Fi-equipped Nokia mobile phones to make internet-rate phone calls (VoIP calls) over Wi-Fi connections. When the handset is not in Wi-Fi range it reverts from being a 'Truphone' to being a normal mobile phone, so people need only one phone.

'On-net' Truphone users show as 'online' in Google Talk, enabling people to know exactly when they can make a free call. Calls between Google Talk and Truphone are free because they are pure VoIP calls and take place entirely over the internet. Communication between Google's servers and Truphone's servers is via the standard XMPP protocol.

James Tagg, Truphone's CEO, said: "Interoperability between Google Talk and Truphone means the web/mobile VoIP divide has been bridged. Google Talk can call Truphone, and Truphone can call Google Talk." [See here for a video of Google Talk and Truphone in action.]

Truphone is free to download and there are no monthly subscriptions or hidden charges. Truphone-to-Truphone calls and Truphone-to-Google Talk calls are always free; other calls are charged at characteristically low internet rates. Until the end of March 2007, calls from the UK to landlines in more than 40 countries are free, while USA customers can call across the USA and Canada for free.

The Truphone website - www.truphone.com - enables customers to edit their account settings, including: customising voicemail settings, changing the GSM number to which inbound calls are forwarded when they are not on-net, and changing PIN numbers.

Truphone announced its beta software for Wi-Fi-enabled Nokia mobile handsets in September 2006. Currently Truphone is available for Nokia's E60, E61, E70 and N80 Internet Edition handsets.