The release includes the Xcode IDE, iPhone simulator, and a collection of additional tools for developing applications for iPhone and iPod touch.
Generally, Apple releases an updated version of the iPhone SDK in tandem with iPhone OS updates. This time is no different, as iPhone SDK 3.1 has arrived in tandem with OS 3.1 Software Update for iPhone and iPod touch. The update, although not packed with new features and enhancements, does bring over a dozen changes to the software. According to Apple, these are the key features and updates incorporated with OS 3.1 for iPhone.

– Improved syncing for music, movies, TV shows, podcasts, and photos
– iTunes U content organization
– Redeem iTunes Gift Cards, codes, and certificates in the App Store
– Display available iTunes account credits in the App Store and iTunes Store
– Save video from Mail and MMS into Camera Roll
– Option to “Save as new clip” when trimming a video on iPhone 3GS
– Better iPhone 3G Wi-Fi performance when Bluetooth is turned on
– Remotely lock iPhone with a passcode via MobileMe
– Use Voice Control on iPhone 3GS with Bluetooth headsets
– Paste phone numbers into the keypad
– Option to use Home button to turn on accessibility features on iPhone 3GS
– Warn when visiting fraudulent websites in Safari (anti-phishing)
– Improved Exchange calendar syncing and invitation handling
– Fixes issue that cause some app icons to display incorrectly.

In order to access iPhone SDK 3.1 and additional technical resources and information from Apple, users must log in with a valid iPhone Developer Apple ID and password. If you don’t have one, register now.