The fourth beta version of iOS 9 has been released by Apple, alongside a new beta build of WatchOS 2. The new iOS 9 build arrives as 13A4305g and runs on all supported iPhone, iPad, and iPod touch hardware.
Currently, the iOS 9 beta 4 release is available only to registered iOS Developer participants, but typically beta releases get pushed out to Public Beta users soon afterwards.
Those who are currently running a prior version of iOS 9 beta can find the update available now though the Software Update mechanism on their device, accessible via Settings > Software Update. The OTA download weighs in around 362mb, and completing the installation will reboot the iPhone or iPad automatically.
Always back up a device before updating system software.
iOS 9 features improvements to performance, and includes new functionalities and apps, like News app, much improved multitasking for iPad with split screen view, and the use of a new system font called San Francisco. iOS 9 will be released to the public this fall.
Separately, WatchOS 2 beta 4 has also been released for Apple Watch users, the update requires a configuration profile on the paired iPhone to install as usual. iOS 9 beta is required on the paired iPhone to successfully install WatchOS 2 onto an Apple Watch. The WatchOS 2 beta 4 build is 13S5305d.
Developers will also find Xcode 7 beta 4, along with a new version of OS X El Capitan 10.11 beta 4 to download and install on their Macs.