I have a FM transmitter that I was using to Play my Rio MP3 player wirelessly thru my car radio. I decided to try it using my Treo 600 and PocketTunes and it worked perfectly. While I was listening, a call came in (ringing over my car radio), so I answered without unplugging the FM transmitter. The caller could hear me and I could hear the caller!! The phone was sitting face up on the passenger seat next to me. There was an echo problem from the caller hearing her own voice on my speakers, but it went away when I lowered the volume slightly. The FM transmitter was $19.99 and I bought it from a place here on Long Island called MicroCenter. I'm almost sure Radio Shack sells something similar.