I have downloaded this application from playstore and I was using this application form more than 6 months and like this application. Databack app saves upto 20% of your mobile data everyday. You can also win some bonous from spinning the daily wheel. This application also provides data monitor facicility which tells you which of your app uses maximum mobile data.
This app gives you the free data recharge packs from the data you save. You will also get 50 Mb mobile data for every friend who joins on your invitation. I have done three recharge through this app till now.