Android
Marshmallow comes with many new features and one of the best feature is "Doze" which stops apps from using the network when your phone is idle .
But now you can get this feature by
Installing Doze App on Devices running Android 4.1 Jelly bean and above . This app work amazingly and it prevents your apps from sending or receiving data without disabling your Wi-Fi or 2G/3G/4G data .
Download Doze -
Play Store 
This apps is not like normal battery
saver , It is very useful and will
surely increase your phone's battery
life .
This application has many options , You can download this app from play store.