We already covered the WaveBoarder application, which is a helper application to Google Wave. The gadget makes it easier to navigate in Wave with the iphone and mean you only have one place where you can work with it. The gadget is available on itunes.
The video I created can be seen bellow.
I feel the application has been user friendly. If that is because HTML version for the iphone has been improved. But the whole experience works much better now. So it could actually be an application you can use for something useful.