I know I have all my Contact birthdays set up as a Calendar Event with a recurrence and a reminder and all I need to do is just make that call, send that email or text message.

Birthday SMS on the other hand is an application which “allows a user to set up time when the device will wake up and check if there are any birthdays <...> and if there are then it will send a user configurable message to that contact”. I know some will say it’s lame and lazy but I really like the idea in this busy world we’re living in. Just set up the message template and the times to check and you’re set.

Also, in case you have many Contacts and haven’t managed to add Calendar Events with Reminders to all of them, this application will also allow you to add Contact birthdays the Calendar as an appointment.

(Source: XDA Developers)