Updated README

README.md

@@ -1,10 +1,18 @@
-# NodeSOS MQTT
+# NodeSOS MQTT (For Home Assistant)
 
 [![Version][version-shield]][npm-link]
 [![License][license-shield]](LICENSE.md)
 [![Type definitions][type-definitions-shield]][npm-link]
 
+This application provides an MQTT client that interfaces with
+[LifeSOS](http://lifesos.com.tw) alarm system.
+It will publish the state of all devices to an MQTT broker, which can
+then be consumed by [Home Assistant](https://www.home-assistant.io). It will also subscribe to topics on the
+broker that allow the control of the alarm system (e.g. arm, disarm) and
+turn on/off device features (e.g. bypass, home guard etc.).
 
+It was written for & tested with the LS-20/LS-30 model, though it should also
+work on the LS-10 model.
 
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