Here is a video showing Scott using the Pecs board.
I have loaded sound files onto the board so that he learns how to use the keys. And with music, everything works.
The advantage is that the buttons are assigned to individual mp3's, and you can then easily exchange them. You can also use any language for your PECS. If you don't want to record the words yourself, you can also use text to speech and download them as mp3's.
This is the first prototype. There are still some improvements needed, but as you can see, it works.