I installed a P.I.E. X3 unit in my '05 Pilot. It has three aux inputs. There is a little switch for changing from one input to the other. Post a question on the P.I.E. forums and ask if they make an X3 or similar device that would interface with the Ridgeline head unit. Also check with logjam (
LOGJAM ELECTRONICS.COM. They are an authorized P.I.E. dealer, amd may have other prodcts of interest.