Sure!  If I understand you correctly, Processing won't be running at all while you are typing.  Therefore, Procesing can't do anything to help you and this might be a better question for the Arduino community. Try taking a look at the following threads, or post a new one to the Arduino boards if they do not help.  In short, it looks like the Arduino will receive your keyboard input over Serial (as it receives many things) and then you can interpret it on the Arduino. What I cannot quite tell is whether this will only work when typing into the serial monitor of if it works in general.  You might need something known as a key logger.  Again, the Arduino community will have a better understanding of the ins and outs.  Admittedly, it's been a while since I had an Arduino on my desk.