Capture key & key combinations from keyboard

Let's say I have a window-less application which has only an icon on the Taskbar (Windows, Mac OS X & Linux). I want it to capture some key & key combinations, let's say Right Control + Right Shift. Upon keying in correct, combination, it will do something, say take screenshot. I can do window-less app, icon on the Taskbar and screen capture but I don't know how to monitor keyboard globally for key combinations. Please kindly advise. Any help or hint is greatly appreciated! Thanks in advance!

I don't think there is anything in Qt to do this but have a look at hotkey.cpp. There are implementations for Windows and Linux in the drop down list of files.

Or, use this:
http://doc.libqxt.org/0.6.0/qxtglobalshortcut.html

Thank you very much numbat & tbscope. Your prompt responses are very appreciated. Let me have a look at the pointers.