Sphinx Search is a plugin that uses the Search API plugin and Sphinx as a backend for searching. It searches comments, posts, and pages and also allow
Sphinx Search is distributed as another example of the Search API project and uses Sphinx has a backend for searching.
The plugin requires some additional server side work (installing and configuring Sphinx, a cron job, etc.), so it should only be used by advanced users. Details on how to install the plugin can be found on the Installation page.