Check out Griffin Technology, who makes a foam iPhone/iPod cup holder adapter that will hold your iPhone snug in the cupholder. I just set my iPhone in the back cupholder, which works great for me...
This worked when I last did it (2 years ago!) using a Powerbook G4 running the "Tiger" version of the OS. I believe the functionality was removed in the transition to the Leopard version. There is a 3rd party software program, "Prius Phonebook" - see Download Prius Phonebook 1.0.1 - Transfer your Address Book on a MacBook using the built in hands-free system on the Toyota Prius. - Softpedia I noted some bad reviews, but the reviewers could not get it to run. One was using Tiger. I was able to launch it (Intel MacBook running Leopard) but was not near my car so could not test it. It probably requires Intel/Leopard, since it did not launch on a PowerPC/Leopard machine. Please let us all know if it works.
I transfered my address book with this program. http://priuschat.com/forums/file-li...-book-transfer-using-laptop-6.html#post813887