Ecosync

Ecosync is an app that turns automatically off the autosync option of your mobile device when the screen goes off and vice versa.
Simple as that.
Disabling autosync is useful to save battery, but be careful, some apps need this option to be enabled in order to function as they are meant to.

If you'd like to have more options, check "Where are you?" app here:
https://play.google.com/store/apps/details?id=com.francesco.wru