Krify Phone

Free audio/video calls and text messaging
* high definition audio and video calls
* audio conference calls with various participants
* pictures and file sharing
* Linphone accounts reachable at any time, even if the app is closed (thanks to push notifications)
* secure communication (encryption options)
* compliant with a large number of SIP-compatible VoIP service providers allowing to reach everyone that has a "classic" phone line.