Programming system shortcuts.

Hi all,

first of all I am sorry for bad english. I will try to write as well as I can.
I use different languages to create my applications (Python, Obj-C and so on); it is possible to create a shortcut for an application which is active even if the window is not focused?

I think (or I hope :D) there's a way to create a system shortcut which can trigger an application function. Is this possible?

Any help would be very appreciated. Thank you!

—Albé