Google recently added the ability to create a birthday calendar. However, Google didn't give one the ability to send reminders for the events on that calendar. This is the same thing that Apple has done for years with their Address Book and iCal integration. And I hate missing someone's birthday when I don't happen to look at my calendar that day.
I saw this as an opportunity for improvement. I also saw this an opportunity to learn about Google App Engine. So I wrote a python application that lets you schedule email reminders for the Contacts Birthday Calendar. In addition, you can select a specific hour in a specific time-zone to send the reminders at as well. The application use's the Google App Engine user authentication and the Google Data AuthSub permission request API to get upcoming events for display and email reminders.
This gave me some good experience with Google App Engine's scheduled tasks and Task Queues, as well as a chance to hone up on my Python. Without further ado, I present GCalendar Reminders. Feel free to use it to send yourself emails using the security of Google App Engine.