Android smartphones can natively show the battery level of connected accessories and bluetooth devices.
According to XDA-Developers, Google is about to introduce support for Android to have battery status information from a Bluetooth device connected via an API that should be integrated into a future version of Android, perhaps Android 8.1.
Advance support is the “getBatteryLevel ()” function in the “BluetoothDevice” class found by developers of XDA-Developers: through this feature, the device natively (or an app) can ask the connected Bluetooth device how much autonomy Has, and thus make the information visible to the user.
In practice, users will be able to see on their smartphone how much autonomy they still have, for example, a pair of connected bluetoth headsets. However, because the information is correctly displayed, the connected Bluetooth device must support reading and transferring the battery status that it is powered (Battery Service).
There are third-party applications such as BatON in the Play Store that let you know the battery status of your Bluetooth devices, but having this integrated feature in the operating system will make it unnecessary to install additional applications.
There are also official applications provided by bluetooth accessories manufacturers that can be installed on the smartphone to ‘read’ battery status, but as above having this system-level option without having to install additional apps is preferable to not ‘weigh’ Device itself.