If you have got your Google wave invite then you might like Google wave notifier. Its a firefox add-on that alerts or notifies you for unread waves in your inbox. Google wave notifier checks for unread wave messages, arriving in your inbox, on a time interval of your choice.
Once you’re done with settings, google wave notifier will start checking for new incoming waves after every fixed interval of time as set by you. For any unread waves it puts a number in your status bar.
Double clicking on the wave icon will take you to your Google wave account straight away. This addon has been tested on and is fully functional with Firefox 3.x.x.
Recommended reading: What Is Google Wave, How to get Started With It