Physical interactivity?

I really enjoyed both readings on interactivity and the current and future states of interactive design ( chapters 1 & 2 from The Art of Interactive Design and  A Brief Rant on the Future of Interaction Design ) Both pieces encouraged me to think about what interactivity really is and what makes a good interaction.
How would I define physical interaction?

I do agree, for the most part, with Chris Crawford’s assessment that Interactivity centers on the three actions of Listening, Thinking and Speaking (or input, process, and output). So physical interaction or interactivity, to me, would be to replace listening and speaking with some sort of mechanical motion and a response in kind. I’m reminded of Newton’s 3rd law of physics, the law of reciprocity; if I push a box, the box pushes back on me. I think that a large differentiator between good and bad interactivity would be the matching of the response to the action.

I think a poor example of this would be an interaction of the phone in my pocket. If I press and hold my finger down, a small motor inside the phone vibrates. This doesn’t mirror the effect of a real object. A real object could move, depress or flex in response to touch.