This is something I thought you might all be interested in that was posted over at SineApps.
Ward Mundy has posted details of his Free Asterisk Telephone Reminder System:
Introducing Telephone Reminders 2.5: The Free Asterisk Telephone Reminder System
http://mundy.org/blog/index.php?p=117
Excerpt: Using nothing but a phone call, you can schedule reminders for the near or distant future, specify different numbers for the return calls, and customize a recorded message for each call. In short, it’s perfect for appointment reminders, birthday reminders, anniversary reminders, and anything else you want or need to remember.
Ward Mundy