So I was writing some e-mail the other day. A long one. At the beginning I said, in the text, that some document is attached. Then I went on writing the rest of the message and kind of forgot about it. When I was done with the rest and wanted to send Gmail popped up a message asking me if I still want to send or attach my document. I mentioned that I wanted to attach something.
Smart program. So they read my message, found the words attach and reminded me that I still should do it. A little detail, but very useful.