The app is basically a mobile version of the My O2 section of the O2 website, in that you can see what you've get left in your included allowances, and how much your bill is to date.
The My O2 app is free and works for both Pay Monthly and Pay & Go customers, although business and corporate customers can't use it just yet.
To access the app you'll need to enter a four digit PIN, so you don't have to worry about people getting their mitts on your info if they manage to get their hands on your phone.
O2 has said it is looking into providing other phones with a similar app, but isn't ready to announce anything as yet – we'll keep you posted on any news on this.
Until then, be sure to check out our hands-on blog with the app for more details, and let us know what you think to it below.