Apple has released Xcode 4.3 (http://macte.ch/14CEo), an update of the developer tool for creating apps for the Mac, iPhone and iPad. Xcode is available to members of the Mac and iOS Developer Programs from the Apple Developer website.
Version 4.3 offers support for Mountain Lion’s new Gatekeeper app security feature (http://macte.ch/7yDaw). It requires Mac OS X 10.6.6 or later and is a 4.25GB download.