RakEM, Raketus Extended Messenger, app allows free Secure Messaging, Picture Sharing, voice and video calling (groups too), and voice and video messages over 3G, 4G, 5G and WiFi. You can also delete your chats from your device and your friends device all at once or selectively message by message (unsend your messages).
RakEM uses direct device-to-device technology, so messages go directly from your device to your friends device, without going to a server - no server touch-downs. Your messages are private and secure with RakEM.