Multitasking

iOS 4 delivers seven new multitasking services that allow your apps to perform tasks in the background while preserving battery life and performance. These multitasking services include:

• Background audio - Allows your app to play audio continuously. So customers can listen to your app while they surf the web, play games, and more.
• Voice over IP - Your VoIP apps can now be even better. Users can now receive VoIP calls and have conversations while using another app. Your users can even receive calls when their phones are locked in their pocket.
• Background location - Navigation apps can now continue to guide users who are listening to their iPods, or using other apps. iOS 4 also provides a new and battery efficient way to monitor location when users move between cell towers. This is a great way for your social networking apps to keep track of users and their friends' locations.
• Push notifications - Receive alerts from your remote servers even when your app isn't running.
• Local notifications - Your app can now alert users of scheduled events and alarms in the background, no servers required.
• Task finishing - If your app is in mid-task when your customer leaves it, the app can now keep running to finish the task.
• Fast app switching - All developers should take advantage of this. This will allow users to leave your app and come right back to where they were when they left - no more having to reload the app.

iAd

Apple's new mobile advertising platform, combines the emotion of TV ads with the interactivity of web ads. When users click on mobile ads they are almost always taken out of their app to a web browser, which loads the advertiser's webpage. Users must then navigate back to their app, and it is often difficult or impossible to return to exactly where they left. iAd solves this problem by displaying full-screen video and interactive ad content without ever leaving the app, and letting users return to their app anytime they choose. iOS SDK 4 lets developers easily embed iAd opportunities within their apps, and the ads are dynamically and wirelessly delivered to the device. Apple will sell and serve the ads, and developers will receive 60 percent of iAd revenue. Learn more

Game Center

The iOS 4 GM seed software and SDK includes a developer preview of the GameKit APIs that allows you to create apps that will work with Game Center, Apple's new social gaming network. Your users can invite friends to play a game, start a multiplayer game through matchmaking, track their achievements, and compare their high scores on a leader board. The APIs are available to you now and Game Center will be available to iPhone and iPod touch users later this year.