It is a simple battery check app.
It is safe because it does not require special privileges
BATTERY_PROPERTY_CURRENT_NOW
BATTERY_PROPERTY_CHARGE_COUNTER
BATTERY_PROPERTY_ENERGY_COUNTER
BATTERY_PROPERTY_CURRENT_AVERAGE
BATTERY_PROPERTY_CAPACITY
You can see the value.
(For more information https://developer.android.com/reference/android/os/BatteryManager.html)
※ In some terminal there is that the value will not be displayed correctly.