Magic Battery is an application that shows in the menu bar the battery level of all input devices that are connected via Bluetooth. You can choose between a detailed view or an icon-only view. In the detailed view, the battery level is shown next to the device icon. In the icon-only view, the battery levels are shown once the menu of the app is opened. The connected or disconnected devices are detected automatically. The view is then adjusted accordingly. You receive notifications when the battery level of a device is below 15%.