Just ran into this tidbit :

"We have completed the Audio Auxiliary Input for use with the XM
radio addition and will make it available soon. It is something that
can be added later after the installation of the XM unit with
minimal disassembly and will provide direct input to the radio for
left and right audio signals. You can use them for your portable
players or whatever audio you are trying to add. This will be
something that factory XM radio owners can use or owners of Prius
who have had the 6 CD changer added to their base system. The aux
input is installed and operating at this time in our Prius and
provides clean high quality audio.

Happy Monday
Coastal Dave
www.coastaletech.com"