The developers on the Gmail team add a new feature to Gmail Labs: a forgotten attachment detector. With the experimental feature enabled, if you mention an attachment in your email and hit send without actually attaching a file, you'll get a pop-up message asking if you meant to send without the file. This new feature supplants the Attachment Reminder script in Better Gmail, though the words the reminder used as triggers were configurable, and these are not. (In fact, I haven't tested the Gmail Labs version in languages other than English.) My initial test show that it works sometimes—an attachment-free message that read "File's attached!" didn't trigger a confirmation dialog, but the words "See attached file" did.