If I remember correctly, someone used a USB stick with a blank MP3 file (ie several minutes of nothing) and an adapter to do this on the early models.
From what I remember, the cable has 3 sections (phone, CD Changer and I want to say aux) but the Blue and me system is only using the aux and phone input but covers all 3 ports. I was going to try getting a splitter and use the cd changer feed but never bothered. Just made do with an USB stick. It's always there, doesn't need charging and is small enough to remain pretty much unseen. It's also colour coded to interior (balck and red)