Simply displays a red indicator on the minimap that warns you that the minimap is zoomed in. The little number (see screenshots) is the current zoom level (1–5).
If the minimap is completely zoomed out (zoom level 0), the indicator goes away.
Adjust size, font and position to your need. By default, it is anchored to the Minimap frame and should also work with minimap mods, as long as the mod does not replace the Minimap frame with a custom frame.
The CPU usage of this Aura should be near zero, as it is only triggered when the minimap zoom level actually has changed (event "MINIMAP_UPDATE_ZOOM").
If the Aura is unable to retrieve the zoom level value (for whatever reason), it will display a warning text. So if you don't see anything (no indicator and no warning text), you can be sure that the minimap is zoomed out.