SwipeBright is a new jailbreak tweak under the BigBoss repo that allows you to simply swipe your status bar to adjust the brightness. You just swipe to the right to increase the brightness or you can swipe to the left to decrease it.
If you open up the tweak's settings, you will see some options that you can adjust the way you like. Starting from the enable-on-lock-screen button and the activation method and moving to the sensitivity.
The main downside of this tweak is that it coasts $0.99 and it is too much for a simple tweak like that.