MacRumors has screenshots of Apple's new iPhone Push Notifications (running through the new iPhone 3.0 software).
Think of it as the real-time feed (or stream) going mobile. Just as Facebook's feed opening sparked new innovation and successes, push will do the same. And also like Facebook, developers and applications will have to walk the fine line of too-much vs. too-little information (usually solved by customization / personalization):
