Early on, Google has announced the intention to open source Java Robot API. Now it has finally arrived.
The google code project has existed for sometime, but it only contain documentation before. Now it also has the source code. :)
For wave gadgets:
You may not want to update the gadget ui when user interact with it, you should just generate a state change, then wait for the state callback to change ui.
Seth demoed a +1 gadget. He also demoed a wave gadget being embedded on igoogle using embed API.
Wave is indexed in realtime. There is indexer watching change and update index for your search.
Hook extensions
Robot architecture