It appears that no slave unit is required. However, double check your application with them before ordering. For kicks (evethough I traded the truck in) I see at
http://www.logjamelectronics.com/piegm9aux.html
that a converter is available for a 2001 Denali with a footnote that these adapters will not work with a six-disc in-dash cd-changer, however; all Denalis come with this changer. I emailed them and they responded that the converter will not work with the Denali whether the cd-changer is removed or not. I'm sure if you don't have one of these weird exceptions that it should work.