Well, this is interesting, no?
[EDIT: there's now an interview in the Guardian with the inventors:
Why the banana and the pizza box?
In the invoked computing scenario, the object itself works as an "invocation" trigger and supports interactivity. We naturally looked for trigger-objects that are more or less pervasive in the real world, hence food-related items (the banana and pizza box). As triggers, they operate in ways similar to icons in a computer operating system: these are not the applications themselves, but keys to open them, to invoke them. On the other hand, real physical objects become the support for the interaction, provide surfaces on which to project images or sound.
As one reader points out, Techcrunch did give a better description of the process, though. ]
Duration: about three minutes