Near the end of the video you can hear his "I am hungry" cry. It's distinct from his cries where he's upset or uncomfortable, so Alisha and I have learned to distinguish it. It's neat to be able to start communicating with our boy!
If you're wondering what kept his attention so well, it was a printed piece of paper. I downloaded some high-contrast pictures to get his mind stimulated, then combined them on a sheet of paper. I rotated the piece of paper every once in a while to keep things interesting. Here's what it looked like: