What would be the best device for an IPhone?

My boyfriend has an IPhone and he has been talking about how he wishes that he could have something to listen to his music directly from his radio from his car. His birthday is coming up and I was hoping to get him a device that would work well. I know of transmitters for some channels but all I've heard is that they are not that good at all. His car only has a CD player no tape player. I was wondering if there would be any other device that I could get that would work in this case. I was also hoping to find a device that would help it stay charged at the same time. I'm very doubtful but any information would be great. Thank you.