The headset that came with my Treo 600 broke, so I brought it into my Sprint store. They gave me a little black headset with 2 earpieces, with the mike in the middle between them, and with a little call off button on the mike.
Calls would come in through both earpieces, and with Freedom and Pocket Tunes, the music would come in through both earpieces (I don't know if it was stereo, or the same channel on both). I lost the headset, and I cannot find anything like it! I bought the Treo 650 hybrid headset, and it does not work at all. The headset did not have a switch on it - it switched automatically with Freedom. It came in a tiny ZipLock bag. It may be another phone manufacturers headset. Help! I know it is out there! Does anyone know anything about this headset?