DataMan app. This time by MacStories.
"DataMan is probably the most complete app to monitor and even geotag your daily, weekly and monthly data usage on your iPhone. If you care about having detailed results about your data usage on the iPhone, you might want to give this a try."
Thank you Federico Viticci from MacStories. DataMan is going to get even better when 2.0 is out. Read the full review.