The App Magic Battery shows the battery level of all input devices that are connected via Bluetooth in the menu bar.
By now only Bluetooth Input devices from Apple are supported.
You can choose between a detailed and an icon-only mode. The detailed mode shows the battery levels right in the menu bar.
Receive a notification when the battery level of an input devices reaches 15%. You should charge your device after you receive this notification once the system is shut down.
Connecting or disconnecting a device is detected automatically. No additional setup is required!