On Android 4.0 and above, there is a feature called Data Usage, which is to show the data used per application over WiFi or SIM card. Background data usage can be also tracked from the Data Usage menu. To see how much data have been used per application, do as follows:
1. Open Settings app and go to Data Usage.
2. Set the data usage cycle
3. Now scroll down to see the list of applications which had access to internet in the given time period.
4. Tap on each application and scroll down to see the amount of data transferred in the background