You cannot directly access the system feature in your PhoneGap app to extend its functionality.
PhoneGap provide various plugins that allow accessing features like – camera, geolocation, contacts, battery status etc.
You can easily add plugin using NodeJS.
Plugin implementation is different for each platform.
In this tutorial, I am adding the battery-status plugin to PhoneGap android app. That gives battery level status of the device.
To deploy the application I am using PhoneGap Build.