How can I play music in my car from a USB key?

Yvette has a USB key with music on it and she wants to play it in her car. Leo says that some cars come with USB options, but Yvette will probably need a third party head unit radio that will support that. Or, she can get a small computer that plugs in. Satechi mades the Soundfly, an MP3 player that supports USB drives. It comes with an FM transmitter built in.