iPhone OS 4.0 is a big upgrade to the iPhone OS. Here are some of the 4.0 APIs you can now use in your application:
• Multitasking—You can now run multiple third-party applications at once.
• iAd—By taking advantage of the new iAd framework, you can make money by serving Apple-approved ads to your users.
• Game Center—Do you want to build a multiplayer game? With Game Center, you can easily add matchmaking and leader boards to your game.
• Local notifications—Local notifications give you the ability to display an alert to the user even when your app is running in the background. For instance, alert your the user when a message arrives in your chat application.
• Event Kit—Access the user’s calendar data.
• Quick Look—Use the quick ...