Knockr allows you to launch apps with a gesture from anywhere.  With Knockr and an OLED device, like the Samsung Galaxy S5 or the Moto X, you can open apps with a gesture when the screen is off.  If you don't have an OLED device you can still use Knockr, just check the 'Lockscreen Only' option in the settings and Knockr will become your lockscreen and you can open any app straight from the lockscreen.  Knockr Everywhere add a floating button to your screen that when clicked will open the gesture listener so you can launch an app from anywhere at anytime.  Knockr also has Tasker Integration which gives you even more control of Knockr.  Use Tasker to set the parameters you want for Knockr to open/pause/close.  Currently only the Knockr 'off screen' feature is integrated with Tasker.