Snapchat - Real-time picture chatting

Wave X - Share emotions in one gesture

Element.io - Secure messaging app with strong end-to-end encryption, advanced group chat privacy settings, secure video calls for teams, encrypted communication using Matrix open network. Riot.im is now Element.

Knoto - Send photos to friends automatically using face recognition

StealthChat - StealthChat is Encrypted, Private, Secure Calls and Chats on Android and Apple iOS

Postpone Pixel - Send a photo to yourself or a friend in the future