David Chalmers gave a TED talk in May of last year. It's on a really fascinating topic: the extended mind thesis. (Chalmers co-authored an article on the topic that you might also find interesting.)
His example of a smart-phone is an interesting one. He notes that my phone stores memories (e.g., phone numbers) and serves as an "executive decision-maker" (e.g., helping me find a good restaurant). Chalmers thinks that my phone is actually part of my mind and not merely a tool that I use to form my beliefs, desires, etc. Indeed, his view is that a great many objects in one's environment are part of one's mind. Consider things like address books, Google, Facebook, GPS devices, and the various lists we make like "to do" lists and grocery lists. The upshot of Chalmers' view is that the mind "ain't all in the head."
I wonder what you think about his talk, his arguments for the extended mind thesis, etc.