Nokia has slowly been patching the holes in Windows Phone 7 functionality and features with their own exclusive apps.
The latest is Nokia Network Usage, an app which lets you monitor your carrier usage (Phone, SMS and Data) on a monthly basis so as to avoid overage charges.
The app also provides useful information, such as detailed usage data and who your most used contact is, which can be helpful for special Friends and Family calling plans.
The app will also notify you if you are close to your usage limits.
The app is not available yet, and we do not know when exactly it will show up, but it is expected soon.