I am looking for a solution to be able to buil an Extranet based on EE, but am missing full text search for attachments. I follow developments in this area and found an interesting project called xapian. There is interesting work done in this field for Drupal, which can be found at http://drupal.org/project/xapian, done by Trellon http://www.trellon.com/blog/xapian-search-drupal
Info about using xapian and php can be found at http://xapian.org/docs/bindings/php/.

Does anyone find this interesting?

I would be ready to pay for it… ;-(

That would probably require a module, not an extension. Just saying.