NOTE: The app needs the phone to be rooted and running 5.0 Lollipop or higher

Wear Battery Control is an app to switch On or Off the battery saver on your phone, when your phone is at low battery level it kicks a mode called battery saver which reduces the 3G working time, GPS, WiFi, using this app you can switch on or off the battery saving mode

Source code: https://github.com/KonradIT/WearBatteryControl