Well-known hacker Stefan Esser, also known as i0n1c, has posted a new proof of concept video showing an iOS 8.4 beta 1 jailbreak running on an iPhone 6. In the video, which shows Cydia prominently showcased on the Home screen, he shows off the Apple Watch companion app, and the newly redesigned Music app to prove he's on iOS 8.4 beta 1.
i0n1c is a talented hacker, and based on his past body of work, we have no doubt that this demonstration is real. Just don't expect a public jailbreak for iOS 8.4 or any other firmware to come from i0n1c. This is for his personal work, and he's very proud of his work, hence he is showing it off in this dazzling new video.