AnnivSS

My mom has a 2005 GMC Envoy Denali with Navigation and shes just wanting an aux audio cable input to play her ipod through. Shes not interested in controlling the ipod with the factory stereo or anything of the like. Whats the cheapest and easiest way to go about doing this? Ive been looking a bit and keep finding kits to make the ipod control through the head unit and steering wheel controls but nothing about a basic aux input.