Greetings Richard -
Actually, no one has tried to use these two together yet. Or at least, if they have, they haven't shared. We have had at least two people use this tool in place of the category module.
They did this by creating a menu that had each category as a link that was to a predefined search. If you check the SOBI2 homepage, there is a list of special links, including the syntax for searches. By specifying the category in a link, the page comes up as if it were a search. The users then have the search box at the top (unless disabled in the config) and the map on the side. That looks like a good workaround. Other than that, we haven't done any real integration on these two.
The other suggestion might be to have the category module embedded the way the search map is embedded. I know it is designed to work in a standard Joomla module position, but perhaps it could be embedded inside a floating div?