Where is my mind?

In the LRB, Jerry Fodor reviews Andy Clark's Supersizing the Mind: Embodiment, Action and Cognitive Extension:

The best way through Clark’s book is to start by reading the foreword by David Chalmers and the paper by Clark and Chalmers that is reprinted as an appendix. These are short, informal presentations of the so-called ‘Extended Mind Thesis’ (EMT), of which the rest of the book is an elaboration and discussion. Here, then, is a passage from the foreword: ‘A month ago,’ Chalmers tells us,

I bought an iPhone. The iPhone has already taken over some of the central functions of my brain . . . The iPhone is part of my mind already . . . [Clark’s] marvellous book . . . defends the thesis that, in at least some of these cases the world is not serving as a mere instrument for the mind. Rather, the relevant parts of the world have become parts of my mind. My iPhone is not my tool, or at least it is not wholly my tool. Parts of it have become parts of me . . . When parts of the environment are coupled to the brain in the right way, they become parts of the mind.

Similarly, later on in the book, we’re invited to consider the cases of Otto and Inga, both of whom want to go to the museum. Inga remembers where it is and goes there; Otto has a notebook in which he has recorded the museum’s address. He consults the notebook, finds the address, and then goes on his way. The suggestion is that there is no principled difference between the two cases: Otto’s notebook is (or may come with practice to serve as) an ‘external memory’, literally a ‘part of his mind’ that resides outside his body. Correspondingly, Otto’s consulting his notebook and Inga’s consulting her memory are, at least from the viewpoint of an enlightened cognitive scientist, both cognitive processes:

Such considerations of parity, once we put our bioprejudices aside, reveal the outward loop as a functional part of an extended cognitive machine. Such body-and-world involving cycles are best understood . . . as quite literally extending the machinery of mind out into the world – as building extended cognitive circuits that are themselves the minimal material bases for important aspects of human thought . . . Such cycles supersize the mind.

That’s pretty impressionistic; but unless I’ve missed it, there isn’t an exposition of EMT that is markedly less metaphorical in the book. So, could it be literally true that Chalmers’s iPhone and Otto’s notebook are parts of their respective minds? Come to think of it, do minds literally have parts? If so, do some minds have more parts than others? Roughly, how many parts would you say your mind has?