Wow man, top notch work, I even signed up just to say so. I also prefer it over the Celica build because it allows you to pop the tablet out every now and again. I've already started looking for a way to adapt the same style 2007 Imp.
Had a question regarding the Parrot system though. It functions as a low level amp then into the car's existing audio (which isn't rocket science) but in that connection to the car speakers, do you think it's manageable to route it to a real after market "WUB WUB" style amp? I'm purely asking because I haven't worked with the unit at all so I'm just not sure how it jumps into the existing wiring harness.
I'm also asking because I got my Impreza for a steal and the dealership didn't know about all the aftermarket stuff installed - both under the hood and inside the car. For example, all wiring was left in place for an amp, sub, and to route after market speakers (which are still there) into the amp.
Last question would be just an inquiry of how you're controlling things like "Next - Play - Pause - Back". Do you get the external module to control that or are you doing everything from the tablet? I'm looking at beefing up to one of the Parrot modules and integrating the little display that can pair with two devices at the same time so I could pair my phone for calls and the N7 for music (which yours should be capable of doing as well unless there are various revisions to the MKi 9100).
Again, great work man. Out of this world.