As you all know I am a big Google fan! and this is one of the most interesting presentations I've seen.
Google Apps, Google Mail, Chat and all other cool tools are working together in real time.
Google waves was written in GWT and is based on an open protocol so anyone with the ability to grasp what these guys have done, can build their own wave.
Take a look at: http://wave.google.com/ there is a great ~120 min presentation of the cool features.
Among other things you can find integration with Twitter, real time editing, Bug Tracking integration and Multilingual support during all the above - you really need to see the demo - it's somewhere between minuets ~90-120 .