Last modified: 2014-11-07 23:20:00 UTC
Not quite sure how this will work (and how it will know which ones are available), but this would probably be rather useful. https://www.mediawiki.org/wiki/Help:Page_status_indicators is currently blank. :-)
PSI's can contain arbitrary wikitext so ideally their contents would be editable in a SurfaceWidget, however I suspect in most situations they will be transcluded onto the page and therefore not editable at all.