When your iPhone is locked and you receive a phone call, you'll see a slide to answer knob that allows you to respond to the call, and declining a phone call will require you to press the Sleep/Wake button twice. Cou is a new jailbreak tweak that allows you to customize this interface and replace the slider found on the Lock screen with buttons you normally see when you receive a call while the device is unlocked.
Developed by danteseig, Cou replaces the Slide to Answer slider with two buttons called 'Answer' and 'Decline'. This means that you can easily reject a phone call by pressing the Decline button rather than double pressing the Sleep button.