Promised "push notification" still missing from iPhone 2.1 firmware

Apple has released the 2.1 update for the iPhone, and – as widely rumoured – it's lacking the push notification system which was stripped out of the developer 2.1 firmware seeds last month. To recap, this system was touted by Apple as a system to get around the biggest built-in limitation of the iPhone for developers, namely the lack of support for background applications. 

The ability to have applications running in the background is incredibly useful on a mobile phone. Think, for example, of instant messaging or social network services, both of which benefit from being able to poll for updates in the background and alert you if something new comes in.

With the iPhone 2.0 software, though, Apple took the decision not to implement background applications largely for the simple reason that if badly written, they can suck the life out of your battery faster than you can say "Steve Jobs is a fruitarian". Anyone who used the first version of the Jaiku application on Nokia smartphones will know exactly how much impact a background task can have on battery life.

To make up for this, Apple announced it would create a "Push Notification Service" which allowed developers to send messages to the phone without their application being open. For example, suppose you're running an IM service. If a user receives a new message, it's pushed to the phone. The OS then tells the user they've recieved something and they can then launch the required application. Pushed data can take the form of "badges" – for example, updating the icon of an application with the number of waiting messages (much like the email and SMS apps).

All this sounds like a great compromise, but unfortunately at some point in August, the feature was pulled from developer versions of the iPhone 2.1 firmware. This means that the service is likely to miss its previously-announced ship date of "sometime in September".

However, while Push Notifications has been pulled from 2.1 it still looks like it's on the agenda for some time before the end of the year – having announced the feature with some fanfare, it would mean some very disappointed developers if it never saw the light of day.