Google Wifi documentation (#2984)

* Google Wifi documentation

* Update sensor.google_wifi.markdown

source/_components/sensor.google_wifi.markdown

@@ -0,0 +1,40 @@
+---
+layout: page
+title: "Google Wifi"
+description: "Instructions how to integrate Google Wifi/OnHub routers into Home Assistant."
+date: 2017-07-15 21:22
+sidebar: true
+comments: false
+sharing: true
+footer: true
+ha_category: System Monitor
+logo: google_wifi.png
+ha_iot_class: "Local Polling"
+ha_release: "0.50"
+---
+
+
+The `google_wifi` sensor platform is displaying the exposed status of a [Google Wifi](https://madeby.google.com/wifi/) (or OnHub) router.
+
+The sensor is able to report network status, up-time, current IP address, and firmware versions.
+
+To enable this sensor, add the following lines to your `configuration.yaml` file:
+
+```yaml
+# Example configuration.yaml entry
+sensor:
+  - platform: google_wifi
+```
+
+Configuration variables:
+
+- **host** (*Optional*): The address to retreive status from the router. Defaults to `testwifi.here` (other options include `onhub.here` and your router's IP such as `192.168.86.1`).
+- **name** (*Optional*): Name to give the Google Wifi sensor. Defaults to `google_wifi`.
+- **monitored_conditions** (*Optional*): Defines the data to monitor as sensors. Defaults to all of the listed options below.
+  - **current_version**: Current firmware version of the router.
+  - **new_version**: Latest availiable firmware version.  If router is up-to-date, this value defaults to `Latest`.
+  - **uptime**: Days since router has been turned on.
+  - **last_restart**: Date of last restart.  Format is `YYYY-MM-DD HH:mm:SS`.
+  - **local_ip**: Local public IP address.
+  - **status**: Reports whether the router is or is not connected to the internet.
+