using the Birthday Reminder Gadget you can share,search and get reminder.
First have a look on how to install extensions on Google wave here
1. Use this url as manifest url: http://www.voizle.com/BirthDayInstaller.xml
2. Click Install
3. Click Confirm
4. Click Done on the Wave
5. Add the recipients and they can share their birthdays if they think so 🙂