Linphone is an open source app offering free audio/video calls and text messaging. With Linphone, you can be reachable at any time, even if the app is closed, with a WiFi or 3G/4G internet connection.

Linphone key features:
* 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