Its Truphone – that allows you to make VoIP calls on the Nokia Series 60 Mobile and on many other Platforms. With Truphone you can carry only one phone for both fixed and mobile use - seamlessly roaming between Wi-Fi, Bluetooth and 3G - connecting via SIP to the public phone system. You can call free of charge on any mobile phones, any ware in world, if you have gprs or Wi-Fi, on your mobile phone.
What is Truphone? Truphone is a free piece of software that you can download to your mobile phone. It saves you money on mobile calls by routing them over the internet. Truphone is a mobile VoIP application which offers huge savings on international calls to mobiles and landlines, and Truphone never charges you for calls over the Truphone network, no matter where you are. Truphone works alongside your existing phone deal(Plan), so you can keep your number, SIM card and current setup.
Wi-Fi calls to other connected Truphone users are completely free of charge, also calls between connected Nokia, iPhone and iPod touch Truphone users are always completely FREE. From wherever, to wherever.
Using Truphone you can make phone calls via Bluetooth, Wi-Fi or 3G using VoIP technology on mass market phones. Thus you can avail the benefits of carrying a single mobile device with all your contacts (integrates with the phone book of Nokia s60 and with others) while gaining the benefits of IP telephony(automatically detects access points(on gprs), Bluetooth, Wi-Fi, 3G or LAN that are available for making calls). When you move away from the Wi-Fi access point Truphone will automatically transfer the call to the cellular networks. Call free of charge through your mobile phone, any ware in world through Truephone.
So if you and your friends/family/colleagues all get Truphone you can call each other for nothing(free of charge). Worldwide.
If you are Nokia user like me than to chose your Nokia phone and to download Truphone on that Click this http://www.truphone.com/nokia/download.html#phones
For more phone options you can go to the Home site of Truphone click http://www.truphone.com/ or