Seems buggy as hell at the moment
 
""ALPHA-QUALITY SOFTWARE ALERT
 Download http://web.mit.edu/jhawk/tmp/InDesignImporter-0.1alpha.dmg
and install InDesignImporter.mdimporter into ~/Library/Spotlight. (Or the /Library version if you want to live dangerously.)
 I'm not sure if spotlight will automatically reindex old files.
 
This is alpha-quality software. It's prototyped as a slow and rather painful perl script that walks through the INDD file looking for things that look like strings (generally they start with @-signs), and then outputting them to Spotlight. It will produce some false positives, perhaps things like the names of styles and fonts that are encoded in your InDesign document. It will probably miss some strings. It might even crash the Spotlight importer process (mdimport).""