Have to open a page first to get at the Search bar.
First pass would implement the wagn.org Search bar as something you could drag into Firefox toolbars (Search bars for other Wagns could be generated from this with a little coding effort). Second pass would manage multiple accounts in one plugin, and offer a menu next to it to select which Wagn it should relate to.
Other browsers too of course.
Firefox Add-on of Wagn Search bar+discussed in support tickets
Firefox Add-on of Wagn Search bar+relevant user stories