Apple has released iPhone OS 3.1.3, its latest update to the operating system software for the iPhone and iPod touch. According to Apple’s release notes, the update improves the accuracy of reported battery level on the iPhone 3GS, resolves an issue where third-party apps would not launch in some instances, and fixes a bug that may cause an app to crash when using the Japanese Kana keyboard. In addition, a number of security changes have been made which are listed in this Apple support document. iPhone OS 3.1.3 is available now via the Update feature in iTunes for all iPhone and iPod touch models running iPhone OS 3.0 or later.
Update: Apple has also released an update to the iPhone SDK. SDK 3.1.3 is required for Xcode to work with and recognize 3.1.3 devices. The updated iPhone SDK is available now for registered iPhone developers from the iPhone Dev Center.