Linphone Android client http://www.linphone.org with the custom specifications.
Linphone, Android, Java, Sonim XP7 with Push-to-Talk (PTT), NDK
Setup with Sonim XP7 smartphones with Push-to-Talk (PTT) button.
Using communications with FreeSwitch proxy server.
Rebranding the whole front end with company theme.
Customizations of ASSISTANT and SETTINGS.
Auto provisioning: server address, outbound proxy, and port hard-coded [Server option not available].
User login with username and password.