In App Purchase announced by Apple

Apple has announced in app purchases for iPhone applications. In app purchase gives iPhone developers the flexibility to support a variety of business models.

They can offer their customers additional services and content within their paid app.

The new Store Kit framework provides the functionality to process payments via the iTunes Store. You submit items to the store and set their price. When a customer chooses to purchase an item, your app creates a payment request and sends it to the iTunes Store for processing. After the iTunes Store verifies and approves the payment, your app is notified so that it can provide features or additional content.