The Device Status dialog will show you the status of your input devices. This is only useful if you have a drawing tablet. If you do have one, then you will be able to see and adjust what tool, color, brush, pattern, and gradient are assigned to your different pens (i.e input devices).
To alter the context each device has, simply drag and drop brushes, tools, etc. with the middle mouse button from the respective dialog (e.g you drag and drop tools from the toolbox).
It can be very wise to set up a standard context for all your tools and save it (and disable saving of device status on exit in the Preferences dialog). By doing so you will always have the same settings for the tools each time you start GIMP.