How to display the current mapping for keyboard shortcuts in realtime? Is there an app / script which will listen for keyboard events and display the action that is triggered?

I use Better Touch Tool, and want to run a script on Cmd+F1 but I got the message:


  The key combination "Command + F1" can't be used because it's already used by a system-wide keyboard shortcut. (If you really want to use this key combination, most shortcuts can be changed in the Keyboard &amp; Mouse panel in System Preferences.)


I couldn't find the triggered action until I did a text search on http://support.apple.com/kb/HT1343, and now I'm curious! 

In Sublime Text, it's possible to open Sublime's python terminal and sublime.log_commands(True) to log commands triggered as the keys are pressed… is there something similar for system wide key events?
This program shows all keyboard shortcuts that use the ⌘ (command) key, just by pressing and holding command.
http://www.cheatsheetapp.com/CheatSheet/

It does not show shortcuts that do not include command, but is quick and easy to use.