Realizing that the commercial off-the-shelf OBD-II scan tool wasn't going to work out for this application, I started researching the ways that OEM nodes interface to the bus. I found that they employ interface chips such as the MC33390 which are specifically designed to interface with the bus in a fail-safe manner. In other words, no more jamming of the Class 2 bus while trying to start the engine.
I also found a better microcontroller, the TMS470, that has a built-in Class 2 interface called a C2SIB. This peripheral is much like the UART used for RS-232 serial communications: it takes care of all the physical layer bit-banging in hardware, and presents a byte-oriented interface to the microcontroller. I ordered a demo board based on the TMS470R1A256, and then cobbled together a small daughtercard which would plug into it and provide the physical interface to the Class 2 bus.
While this approach worked much better, the downside is that anything beyond the proof-of-concept would require custom hardware. As I said before, I'm a software guy, not a hardware guy; designing circuits and laying out PCBs is not my forte (as you can readily see from the pictures).
Enter creaseguard, the guy who basically gutted his Z06 and put in an entirely new sound system, CarPC, and other electronics; read his thread about it here. He saw my posts about the HUD One on another forum and offered to design a custom board. After many more months of work, including a several-month wait for some critical parts, this was the result:
I finally had a board with proper connectors for the RADAR detectors and the vehicle wiring harness to plug into, as well as a USB port for future upgrades. WooHoo!!!
Here's a video of the HUD One in action: