Bandyer SDK ( now Kaleyra Video SDK) makes it easy to add video conference and chat communication to mobile and web apps.

With the SDK you may fully customize the communication experience and enclose it in your own application with the least effort possible!

For more details
https://www.kaleyra.com/video

You may check the source code of this application here
https://github.com/Bandyer/Bandyer-Android-SDK