dave-in-nj:
One thing I see that is on the down side is a simple forumlaof cars made - # of cars still working - # of drivers who are not going to want to do anything to the car
That leaves only a few targets for your project.
That said, any modules that you make that can fit would be really cool.
my 1999 Grand Voyager has a gauge cluster with an eyebrow and then a second one above that in which the warning lights reside. a perfect place for a few readouts of systems.
What kinda readouts would you be interested in? We can do a lot just with your OBD2 port.