Telegram Messenger is a free and open source cross-platform messenger with a focus on security. With Telegram, users can exchange encrypted and self-destructing photos, videos, messages and documents (all file-types supported).
Telegram is officially available for Android and iOS (including tablets and no-wifi devices). Unofficial clients for Windows Phone, as well as a Webversion, Mac OSXversion and a Windows desktop client are available from independent developers using the Telegram API.