is an app for both IOS and Android Phones and it allows instant contact to others via your internet settings, either on WiFi if in range and via 3G if outside. For Voice it works like SKYPE and for messages it is like Blackberry BBM or "Whatsapp". It works very well, once installed it checks your phone book and indicates which of your friends already have it, i was surprised just how many of my friends were already using it.
Someone asked "whats the point, I have unlimited texts and 1000 minutes on my contract", well if you are a PAYG then it is well worth it, but even on contract, picture messages usually cost 50p or so on the phone, on VIBER it is free. Other advantage is that if you go abroad and can get the Hotel WiFi then calls home are free contract or not.
Free download, no adverts, nothing hidden as far as I can see....download give it a go, my username is my mobile number which is on my web site.
visit them at www.viber.com