I like the functionality of a hardware camera button. On my Lumia 920 I have a dedicated camera button that I can long-press at any time (in other apps or when the phone is locked) to open the camera app in 1-2 seconds.
I also have a Galaxy Note 1 (JB, rooted) without such hardware button. Is there a way to reconfigure one of the existing hardware buttons (e.g. long-press volume up) to always open the camera app even while the screen is locked?