Here's ver 2 of the hardware
I've already made a v3, to fix a problem with the USB plug on the bottom (for RN52 firmware upgrades). Firmware upgrades will be rare, and in fact, future upgrades will be done via UART pins, so the USB plug is for RN52 modules with old firmware (v1.10 & older). v1.16 and above will use UART for upgrades.
Karlis has done a smashing job on the software side! The module doesn't drop out at all now, steering wheel controls work with both iPhone and Android phones, and he's also integrated bluetooth sync connect & disconnect controls via the head unit (IHU).
There are still some bugs he wants to work out, and of course, getting artist/track info on the SID is on the to-do list :)
You'll also notice the 3.5mm jack at the top. That's for the Mic input to the RN52, which Karlis & I are planning on using the vehicle's On-Star mic. So once we figure out the best way to do that, he even has the code setup to bring Siri up for a long button press :) So eventually, you'll be able to wire in the car's mic to a 3.5mm plug, and plug that into the module, and be able to talk to Siri at the press of a button (or no button if your phone is charging or you have 6S)!
Feel free to ask questions in the comments; Karlis said he'd try to answer software questions for me :)
And no, I'm not planning on making/selling them. Do you know how much work that would be for me for all of you?! But I can help guide you along the way :)