We all use the flashlight on the back of our iPhone from time to time. Previously, we had to turn it on by using an app and turning it on. From iOS 7 however Apple allows you to launch the flashlight in a simple way by pulling down the Control Center (from the bottom of the screen) and clicking on the icon. However, this is still quite tedious for some people, because you have to turn it on iPhone and perform some action. However, a feature has appeared that allows you to turn on the flashlight using a physical button on the iPhone itself.
To do this, you need a jailbreak on your device and a tweak called FlashRing. After installation, you don't need to set anything and everything will work. You can then turn the flashlight on and off using the Mute button on the side of the iPhone. The disadvantage is the impossibility of using the button to mute the phone. You download the application using Cydia, where you add the Source named "BigBoss" and search for FlashRing.
*Source: idownloadblog
It would still require Jailbreak on ios 9.2… it's been taking quite a while :-(