Telegram offers great [apps for mobile communication](https://www.telegram.org). It is based on the [MTProto protocol](https://core.telegram.org/protocol) and has an [Open API](http://core.telegram.org/api). I personally like Telegram for its speed and cloud-support (that makes a web app possible, unlike in the case of WA and others).
Telegram offers great [apps for mobile communication](https://www.telegram.org). It is based on the [MTProto protocol](https://core.telegram.org/protocol) and has an [Open API](http://core.telegram.org/api). I personally like Telegram for its speed and cloud-support (that makes a web app possible, unlike in the case of WA and others).