iOS 8.4.1 Beta 1 Released for Developers
The first beta version of iOS 8.4.1 has been released to users participating in the iOS Developer program. iOS 8.4.1 arrives as build 12H304 and is compatible with the same iPhone, iPad, and iPod touch devices that can run any other version of iOS 8 or iOS 9.
Eligible iOS users can find the IPSW file for download at the developer center from Apple, it will appear underneath the iOS 9 beta release.
Small point releases of iOS are usually aimed at resolving bugs and issuing security fixes, and do not typically contain new features.
At the moment iOS 8.4.1 beta 1 is only available for developers, with iOS 8.4 being the latest stable build for all users. Additionally, there is not a public version of iOS 8.4.1 available yet, though iOS 9 public beta 1 is actively available for any user to opt-in to test. Beta software is notoriously more buggy than a stable build, and is best reserved for secondary devices or advanced users.
Separately, OS X 10.10.5 beta 1 was also released today for Mac developers to test.