Usually found in games or dual-licensed apps, this kind of payment system is used to allow users access to premium-like features only after a fee has been paid.
A demo is included with the download package.
Here are some key features of "iOS In-App Purchases":
· Payments handled via the App Store in-app purchase service
· Management of purchased products
· Can remember already purchased goods
· Supports Apple's "Restore purchases"
· Shows an in-app purchase menu
· Tracks every aspect of the purchase (requests, transactions, restores, etc.)