Text-to-speech is a great way to store passwords on your system. If you use your own audio codec (which will not be updated at the most inopportune moment), then you can always create the same password using the same phrase. But you can change it once a day with the same source text. In this case, if a hacker can copy the system, the saved password (encryption key) will change in a day and that's all! The original text is not stored anywhere.