At the time, Forstall promised that the system would be available for developers come September.

Nor did it make an appearance during January's Macworld Expo keynote. In fact, it pretty much just .

"You know, we're late on this one," said Forstall as he announced push notifications again during Tuesday's iPhone 3.0 preview. According to the Apple VP, the response from developers to last year's announcement had been so enthusiastic that Apple started to think that maybe it had underestimated just how popular the notification system would be. So, said Forstall, the company decided to "rearchitect" the system from the ground up. "Now we're good to go," he concluded.

Despite that seemingly massive task, the capabilities and operation of the push notification system seem to be exactly the same as promised last year. Here's how it works: The iPhone keeps a persistent network connection via the cellular network to Apple's server, through which developers can send three types of notification: a badge update (à la the built-in Mail client), a text dialog (like when you receive an SMS message), or a sound alert. You can also combine multiple types of alert, as demonstrated by ESPN's Oke Okaro showed off a sports application that popped up a text dialog box while playing the familiar ESPN tone.

And that's it.