I've searched for info on this before you start on me. I have a 06 Z4MC. I know there is a retrofit available. I've taken the steering wheel cover off and there is supposed to be a black cable and connector. I can't see such a cable. I have been told that it is possible to splice some cable to wire it in, but thats all I know. Can anyone shed some light on this?

Bump. Curious myself

The cable was included in cars up until September 2004 production, so all you needed was the stalk. Since then, it hasn't been present and you have to splice into the cars wiring. From what I've read, the instructions for modding the wiring are in BMW document 01 29 0 152 661, and should come with the retrofit kit.