iOS 5 is officially launching tomorrow, and the App Store’s review team has been busy these past few days quickly approving app updates that take advantage of the new features available to developers. A first example was OmniFocus for iOS, updated to include the location reminders Apple will make popular with its own native Reminders app. Today another popular third-party app for the iPhone, Tweetbot, has been updated to include bug fixes and a new iOS 5-only feature – Twitter integration.

Whilst we’ll have a detailed overview of Twitter integration in iOS 5 tomorrow, Apple has already announced that developers will be able to use a feature called single sign-on to let their apps fetch Twitter credentials directly from the operating system, which has a new Twitter panel inside the Settings. Thanks to single sign-on, if a Twitter account (or multiple ones) are already configured in iOS 5’s Twitter settings, third-party apps like Tweetbot won’t need to re-authenticate users through a clumsy web view as they’ve been forced to do until today. They can simply get the account-related information from iOS’ Settings app.

So when you’ll install iOS 5 tomorrow, try to add your Twitter account to the iPhone’s settings – this will enable other functionalities that we’ll also cover tomorrow in our overview. Then install the new Tweetbot 1.7, which is already available, and you’ll notice you won’t have to re-enter your Twitter credentials again – Tweetbot will ask you if it’s okay to add the accounts already on your device. The procedure takes seconds, and is managed by an “Import iOS Accounts” option in Tweetbot’s settings. The best part is that because third-party apps are deeply integrated with Twitter in iOS 5, new accounts you’ll add through Tweetbot will also be carried over the system’s Twitter settings.

This kind of Twitter integration with the OS makes for a better first launch experience as users don’t need to go find their Twitter passwords again and re-authorize every account on each Twitter-enabled app. Tweetbot is the first popular third-party client to take advantage of this, and you get it now on the App Store for $2.99.