I have recently started supervising a PhD student who seriously must be the most diligent and polite student I have come across. (Plenty of the other kind around. :-) ) He likes to bring his mp3 player to supervision meetings so that he can record and then play back our conversations when he is at home (although he takes notes too). He commented that it is useful for him to revisit the questions we ask him, and to hear discussion between his two supervisors. I hadn't thought about this before, but it is a good way for PhD students to get an "apprenticeship" to academic ways of thinking. They often need training in the sorts of critical questions other academics will ask them, and help in answering such questions effectively. In a meeting the other day I was asking the student questions to help me get up to speed on his project. Sometimes he couldn't think of how to phrase the answer, so his other supervisor helped him out. The student said it was very useful to listen to answers to the questions again because although he recognised the answers were correct, he couldn't quite put them together when he was on the spot. A good use of technology, I think.