I only have a small data plan, but its enough for me because 99% of the time Im in wifi. But for those times when Im traveling I need this app! AT&T is so bad at letting you know when youre close to going over your data. Data Counter helps keep me on top of my data use, and even though it has to remain open at all times, it doesnt affect my battery life. If you want to take control over your data use, I recommend you install Data Counter.