What I would like to do, is to have a head unit (pref Kenwood) and be able to charge and play my iPhone music through the head unit.

Ive seen some models with USB ports, but do these work ok with the iPhone and charge it ok?

What do other people use, ive seen the FM transmitters for them, but would like a cabled version. Something with a cradle and a cable going to head unit to charge/play would be ideal.