Remaining Credit app

[nikhilr51]

Hi,
I haven't got my iphone yet but i will very shortly and i just wanted to know if there is a program that will tell you how much data and credit has been used as my plan only includes $50 and 100mb which i don't want to go over.

I understand that it has something built in that records how much has been used,
From apcmag.com:
iPhone 3G has a built-in usage meter (found in settings->usage) that tells you 3G/EDGE data, but that, of course, isn't the definitive measurement. It's what the carrier measures on the network-side that they'll bill you on, so it's important to check your usage with the carrier.

I'm not quite sure what that means so any explanation if that will be accurate or not will be greatly appreciated.

Thanks,
Nikhilr51

[nikhilr51]

Anyone?