If you thought iPhone's LED light was just for camera flash, you're mistaken. Of course, Apple put that LED flash on the iPhone primarily for camera flash and secondly for use as a torch (since iOS 7), but what's missing is the ability to control the brightness.
Why on earth would you want to control the brightness of the LED light by the way? I don't know but there could be a variety of reasons ranging from battery-saving to too-much-bright-light. By default, there's no way you can dim the brightness. But if you look into the depths of jailbreaking, there is a solution.
CCFlashLightLevel is a cool new tweak that lets you adjust the brightness of the flashlight. It comes in handy when you want to dim the intensely-bright LED flash.
I like the way this thing got implemented in iOS 7. CCFlashLightLevel works right from within the Control Center's Torch shortcut toggle. If you removed the torch toggle using a tweak like CCToggles, you won't be able to use the functionality of CCFlashLightLevel because it only works on the Torch toggle button.
CCFlashLightLevel is activated when you long-press on the torch toggle in Control Center.
When you long-press, there's a tiny slider overlaid on the torch toggle. Drag it and you will see that the flashlight brightness changes. If you let it go and wait for about 3 seconds, the slider disappears.
You can still use the torch as you would normally: tap on it to toggle on/off. That will make the torch shine in full brightness.
In the preferences for the tweak (Settings → CCFlashLightLevel), you can configure the time for long-press (to show the slider) and the value for timeout. And that's about all one needs.
There's one big drawback to the way CCFlashLightLevel is designed. It was smart to integrate it with the torch toggle in Control Center but I think the slider is unfriendly. The dragger is large enough but since the slider-width is so small, it's not possible to control the brightness to an accurate level very easily. There could be some other way (like laying out a HUD) to make sure sliding to a particular brightness level is easy.
How to Get CCFlashLightLevel Cydia Tweak
The tweak is free on the BigBoss. Search for the tweak in Cydia's search and install it. If you have changed the shortcut toggles in the Control Center, you have to bring back the torch toggle for the tweak to work correctly.