Since AT&T recently started offering capped data plans for iPhone, those of you who were not grandfathered into the unlimited plan do have to pay attention to their 3G and Edge usage. While the iPhone does offer the ability to monitor your usage by going to Settings > General > Usage, it still doesn’t offer a reliable way to see what you’re really using.

Enters Data Counter, a jailbreak application that helps you keep track of your data usage within a given period…

Data Counter is a cellular data counting app that aims at making your data usage tracking easier. You can enter your data plan cap and the start day of your billing period to easily keep an eye on your usage. You can then filter your data usage by date, either with a nice graph chart or with a simple text report.

If you ever go over your data cap, then you don’t have excuses anymore for keeping a close eye on it. Priced at $2.99, Data Counter might save you money overtime. Give it a try and let us know what you think.

UPDATE: You can get a similar application in the App Store for only $0.99. It’s called DataMan [download link].