How do I turn my CD changer input on my head unit into an Aux input for my iPod?

I have a Nissan Maxima with the Bose system, and it has a CD changer input that is not being used . . . since I don't have a CD Changer. I have read that there are products that can convert this connection into an auxilary input for my head unit . . . any idea how to wire this up?