Getting back to the original question....there's an attachment sold by Valentine called the Remote Audio adapter. It can be found at http://www.valentine1.com/moreinfo/Audio.asp

Not sure if you can take this signal (from one of the outputs) and run it into the mute of the Rio Car but it's worth a try.

As far as my rating of the V1, it's money well spent.
Good luck!
Wes