The only wireless headsets that I'm aware of that works with the treos are the Jabra Free speak and Plantronics has one. They work on bluetooth technology and both vendors have one designed to work with non-bluetooth phones (as is the treo).
If interested make sure you get one compatible w/nokia 3000/8000 series phones as the treo uses the same type 2.5mm 4 conductor mini pin
http://jabra.com/products/FreeSpeak_nonBluetooth.htm http://plantronics.com/north_america/en_US...oductName=M1500