Since I had this problem and I'd already posted it as a reply to another PC member, I figured it would be a good place to share this. Toyota Bluetooth Phone This website allows you to check what Bluetooth phones are compatible with your Toyota vehicle's features (i.e. call transfers to and from vehicle, phonebook transfers, etc) for a bunch of different phone manufacturers, service providers, and toyota vehicles. Enjoy!
Seems useful if your phone is listed, but the list is pretty sparse. I have a Treo 755p - which pairs up very nicely with my 2008 Prius, but no information on any Treos on the site.