One of the cool features built into iPhone OS 3.0 is the ability to display alerts and messages from applications that aren't active, also known as "push" notifications. Push notifications aren't active by default, and if you don't have the right apps installed, you won't even be able to find the feature on your iPhone or iPod touch.

To take advantage of Push notifications, you need to start by installing an application that can take advantage of the feature. AP Mobile and AIM both fit the bill.

iPhone OS 3.0 Push notification alert

After you add a Push-aware application to your iPhone or iPod touch, do this:

Install Push-aware apps to see the Notifications Setting

• Launch the application. You'll see a dialog asking if it's OK for the application to use the Push notification service. Go ahead and tap OK.
• Now press the Home button to exit the app and go to Settings > Notifications. You won't see the Notifications option until you install and launch a push-aware application.
• Make sure Notifications is set to On.

Alert settings can be set per-app

Every push-capable application installed on your iPhone or iPod touch will appear in Notifications, too. Just tap each app to turn on or off its sound, on-screen alert, or badge tag. Since these settings are per-application, you can set one to use all three notification type, while limiting another to just audio or badge alerts.

You can set sound, alert and badge notifications

Push notifications are handy because they let users get information without having to always keep a single application open. Instant message clients are especially happy to have Push notification support in AIM and BeejiveIM so they can stay on top of their chat conversations without having to keep the apps open.