Incoming call controls can be modified on jailbroken iOS devices with the tweak Cou. Once installed, Cou changes the steps required to decline an incoming call. Instead of a "slide to answer" slider, the user is presented with two individual buttons, Decline and Accept.
Tapping Decline will have the same effect as pressing the power button twice, which declines the call. This can make it faster and easier to decline a call, however the buttons can also be accidentally pressed more easily. Cou provides a toggle to enable or disable the tweak entirely.