So glad to amuse...
I'd been doubting the CAN thing and yes, I know our cars don't have either ODB variant. There are plenty of things you could monitor (including: timing, throttle position, knock and the o2 sensor (although a narrowband o2 sensor's a bad source of data)) using a simple serial interface...
But again, is it worth it? It's not going to give you near as good an idea of what's going on with your car as an ODB II datalogger would. But, the point still stands that YES something could be made... weak though it may be.