DataCounter

DataCounter is the easiest method to keep track of your data usage in realtime. Whether it is mobile or wifi data. It will display a message after a changeable amount of data has been transferred. This way you will notice when your phone makes unwanted downloads and you can turn off connections.

This is espacially useful if youre visiting another country and you have limited roaming data.
When your WiFi data is limited this is an easy method to prevent your phone from doing unnoticed updates.

It counts data for Wifi and cellular mobile (all possible types - GPRS, 2G, 3G, 4G).

Note:
Continued use of GPS running in the background can dramatically decrease battery life.