It's already possible to 'jailbreak' the iPhone 6S and install whatever you want on it

The first software that can jailbreak Apple's mobile operating system iOS 9 has been released, according to 9to5Mac. The download, which is Windows-only right now, can be installed on the iPhone 6S as well as older devices.

Jailbreaking is the act of modifying an Apple device so the user can install whatever they want on it, including new apps (which aren't checked by Apple), widgets, and other functionality. Developers have been jailbreaking iPhones to add extra functionality ever since Apple released the App Store in 2008.

The act of jailbreaking is an endless game of cat-and-mouse. A developer will find a bug and hole that can be exploited and then Apple will scramble to fix it. Then the developer finds another and and the process repeats all over again, ad infinitum.

The first jailbreak for iOS 9 is what's known as an "untethered" jailbreak, meaning that it continues to work even when the device is unplugged, or after it has been switched off and on again. (In contrast, a tethered jailbreak may only work when the iPhone is still plugged in, and isn't much use for day-to-day use.)

So why do it? It means that users aren't constrained by the App Store. While there are millions of Apple-approved apps available, some don't make the cut - including those featuring adult or potentially illegal content. Additionally, jailbreaking gives users more freedom when it comes to customising their device.