Zentara,
Thank you for the example. It doesn't quite do the trick though. I need something that allows me to open another application even when this is running and your example does not seem to allow this.
Let me explain exactly what I'm trying to do:
I have a Pan/Tilt/Zoom camera control application built with Perl/Tk. I need to use it with a web browser opened to a webcam site. Everything works very well except that when the control application looses focus, the bindings to the keys (up, down, left, right arrows) stop working until the application gets focus again.
A hotkey won't work either unless I change my application to run as a daemon so it can listen to external commands as far as I can tell. I don't want more that one application to run as I'd like to keep it simple and easily portable to other machines.