A few of the key features that help turn your iPhone into a toy for baby: large handles that are easy to grasp, a mirror on the back, and rings on the handles. A clear film over the screen provides some protection and a plastic piece in front of the "home" button prevents baby from constantly clicking out of the application.
What do you think? Is this something you could see yourself using? Although it's not something we'd use often, we could see it being useful for travel.