How to assign a hardware button to camera 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?
You should be able to achieve what you want to do with the help of Home2 Shortcut. The app is self-explanatory. You can easily use it.

If you have enables S Voice on double-tap, go into the S Voice settings and uncheck the Launch SVoice box. This will keep S Voice from launching when you double tap the home button.

Open Home2 Shortcut and configure it to launch the app of your choosing with a double tap of the home button. When you get to the end, after you tap "close" it will ask you to set as default. Select Home2Launcher as the default.

Read more information here.