Waveboard is an app for the Mac (and coming soon for iPhone) that puts Google Wave into it’s own application window. Observant readers might recognise that this is not really all that different from using Fluid or Prism to create a stand-alone site-specific window. Links from the site suggest it is related to Mailplane, a similar concept for Gmail.
Additionally, the demonstrated iPhone application seems to be no different from what Google has already made possible simply by bookmarking your Wave page to the home screen.
If however you don’t wish to worry about setting something like this up yourself you may wish to give it a try.
Waveboard is free software (at time of writing). Waveboard