Looking at Martin's link to using baloo under KDE, the following function calls tracker's sparql query and shows the results in a new frame. A lot more needs to be done and could be added to make this really useful. The results are shown in a file URI format, and find-file-at-point works to open the documents in DocView mode. I use this mainly to use full-text search over a collection of PDF articles (and some ODT/DOCX files). More information could be displayed by modifying the sparql query. I'd love to add something akin to org-mode's hyperlink file display, i.e. return the list of files displaying just the filename and hiding the file URI in the hyperlink - would save column space.
;;
(defun tracker-sparql (sparql-query)
(start-process "tracker-sparql" "tracker-sparql" "tracker" "sparql" "-q" sparql-query)
(switch-to-buffer-other-frame "tracker-sparql")
)
(defun tracker (search-term)
(interactive "sFulltext Search String: ")
(tracker-sparql (concat "SELECT nie:url(?f) WHERE { ?f fts:match '"
search-term
"' }")
)
)