Free presentation helper that shows keystrokes
OS X comes with such a tool.

To activate it, you should go in System Preferences --> Keyboard and select Show Keyboard &amp; Character Viewers in menu bar, see screenshot below.


Then in the top menu bar, ext to the clock, you should have a new icon.

Click on it and select Show Keyboard Viewer, now each time you press a key, the Keyboard viewer will briefly display that key. You will have something similar to this:


I hope this was what you were looking for.