I built it, I use it, I love it. I think it is the best PhatBox interface because it is the only one with buttons 1-6 and disc up/down (also you can hold 1-6 for 7-12 which I have assigned to custom features). It also has a lot of other little UI tweaks that are also found in my Toyota/Scion code (ie: Hands-Free-Seek).
Unfortunately, Pioneer of America wasn't interested, so it never got released. We demo-ed it at CES in 2002.