Documentation for FritzBox call monitor (#779)

* Documentation for FritzBox call monitor

* Category and version number adapted.

source/_components/sensor.fritzbox_callmonitor.markdown

@@ -0,0 +1,31 @@
+---
+layout: page
+title: "FRITZ!Box"
+description: "Instructions how to integrate a phone call monitor for AVM FRITZ!Box routers into Home Assistant."
+date: 2016-08-13 15:00
+sidebar: true
+comments: false
+sharing: true
+footer: true
+logo: avm.png
+ha_category: System Monitor
+ha_release: "0.27"
+---
+
+
+The `fritzbox_callmonitor` sensor monitors the call monitor exposed by [AVM Fritz!Box](http://avm.de/produkte/fritzbox/) routers
+on TCP port 1012. It will assume the values 'idle', 'ringing', 'dialing', or 'talking',
+with the phone numbers involved contained in the state attributes.
+
+To use the Fritz!Box call monitor in your installation, add the following to your `configuration.yaml` file:
+
+```yaml
+# Example configuration.yaml entry
+sensor:
+  platform: fritzbox_callmonitor
+```
+
+Configuration variables:
+
+- **host** (*Optional*): The IP address of your router, eg. 192.168.1.1. It is optional since every fritzbox is also reachable by using the IP address 169.254.1.1.
+- **port** (*Optional*): The TCP port of the call monitor. There is usually no reason to change this.