For the iOS (iPhone/iPad/iPod Touch) app to show background notifications for user messages and other things, we'll need server-side support to manage device subscriptions and send pings off to Apple's servers.
Will also need client-side support to use it.
Version: 1.20.x
Severity: normal
client side is easy (really, really easy). It's the server part that is critical.
I know of two systems that are open source; http://code.google.com/p/apns-php/ and http://www.easyapns.com/php-source but i'm not aware of it's performance and/or featuresets.
Probably best to combine the google and ios push services into one system. not sure which one of them would be the easiest to extend for that.
The backend is done! https://www.mediawiki.org/wiki/Wikimedia_Product_Infrastructure_team/Push_Notifications_Infrastructure
The Android team is rolling this out in their client now, and iOS is starting client development.