It sounds like you're misunderstanding the concept of a zombie. Zombie simonster is physically identical to simonster. On Twin Earth he is also sitting in front of his computer talking about consciousness, and he also emphatically believes that he is conscious. The only difference between zombie simonster and me is that, when zombie simonster says he is conscious, he is wrong.

David Chalmers discusses this possibility in his book, and doesn't believe that it invalidates the zombie argument, but personally, I would prefer to think that the fact that I am sitting here writing about consciousness is somehow related to the fact that I am conscious. I'm still thinking this through, and have been for some time, but I think this requires that consciousness be physical in nature.

I only read the synopsis of the Wikipedia article and am not very versed in this particular model. However to me, the notion doesn't seem to make sense. If you're talking about philosophical zombies, you're acknowledging that consciousness is a real phenomenon, of some sort. If we're sitting here typing about it, we should also conclude that it has an effect on the physical world. So a philosophical zombie, being physically identical to a human but for not having a consciousness, would act differently than a human because it lacks consciousness, which is a real phenomenon with implications on the physical world. (which I suppose you allude to in your second paragraph)

EDIT: Ok I think I see a counterargument. Perhaps belief in consciousness is purely physical, and actual consciousness is just perception of this belief, and a perception of choice in acting on it, whereas our actions are deterministic. Seems like a strange scheme, but I suppose it's possible.

Actually, from the outside, a philosophical zombie would be indistinguishable from a non-zombie. Zombie Chalmers would write books, papers, and opine on the nature of consciousness and his subjective experience exactly as the real Chalmers would.

For a most amusing take on the p-zombie idea, see:

http://lesswrong.com/lw/pn/zombies_the_movie/

(Though humorous, it's the capstone to a series of articles on p-zombies: http://wiki.lesswrong.com/wiki/Zombies_(sequence) )