Using Google to search your content because there are too many security
groups sounds like a bad idea. It would be a good idea to review your
architecture to determine if there are too many constraints. Then review
your search configuration to determine if it is setup correctly.

If it's internal don't you have to have a Google Appliance?

Used the GSA a couple of years ago with SharePoint 2003 and was not impressed.

Not used but read about it on

code.google.com/.../connect\
or_admin/searchbox_sharepoint.html

If you are going for the implementation, please do share your experience here.