TinEye - Reverse Image Search to help find an image's source, duplicates or altered versions.
Misakey - Send encrypted documents & messages to anyone
GImageReader - gImageReader is a simple Gtk/Qt front-end to the Tesseract OCR Engine.
Wire - Private & Secure Messenger
Yandex.Images - search for images on the internet, search by image
WhatsApp - WhatsApp Messenger: More than 1 billion people in over 180 countries use WhatsApp to stay in touch with friends and family, anytime and anywhere.