My framework for familiars allows a builder to set a kind of familiar and name of the familiar on an NPC. I did not get around to writing AI for an NPC to make use of a familiar however. BUT my system can easily be made to work with AI by someone else.
Innocuous Familiars was released in the
January 2013 Custom Content Challenge.
I have a project page for it as wellI have taken this project further for my own uses, but not released it as it requires custom content for the creatures. And I have looked at but not yet pursued doing the same for Animal Companions (what I call Spirit Animals).