This is a shot of the tray icon. You may be just able to make out the green line at the bottom of the icon. As your peak usage increases this will slowly fill up.
Eventually you will have a red icon denoting peak usage has been met / exceeded.

The next shot shows the popup menu. You can see that all usage is immediately visible.
You can also access settings and reports (not yet implemented) from here.

This image is of the settings screen. It is fairly self explanatory. The export functionality is not yet implemented. Email me if you have any feedback, ideas.