Ok, so I was bound and determined to be able to use my 3g Iphone for music enjoyment in my 05 Z71 Suburban.
The FM Transmitters...if they will work at all with the 3g, sound awful. Some cars now come standard with an aux input on the radio to allow you to plug an outside audio device to the car for use with the car's sound system. The new Suburbans have this....but mine (2005) doesnt
So, a little lookin around, I found an aux audio input device which is basically a wiring harness/mess with a box that has RCA audio jacks on it. Hmmmm I said.
Ordered one, proceeded to take my dash apart (that was fun) and wire that beast up....very interesting when your vehicle is equipped with both a factory XM receiver and DVD system (apparently makes things much more difficult). After alot of cussing

and some sweat I got the thing wired up and before putting my dash back together proceeded to test....
Works perfect! Sound is crystal clear, like im listening to the radio
So then I decided I wanted the input jacks to look as factory as possible (I hate hacked install jobs) so I did some dash modding and actually did away with the module itself in favor of just using the circuitboard, thus allowing me to install it directly behind the dash.
End product, aux input that looks factory and sounds great! Take a look, I wish I took pics along the way...but this was an afterthought, so I only have a pic of the finished product:
EDIT: I also found out that I can take a call....the other caller is pushed to the cars speakers (obviously since I am using the headphone jack) and the cool part is....with the phone sitting in my lap I can speak outloud and the other caller hears me just fine!