Goals

At a bare minimum, I need to keep track of, and display, the same information that appears on the current "instrument cluster" of the car.  This list isn't too huge:

• The speedometer is the major one of course.

Also there are two "analog" gauges: 

• Fuel Tank level
• Coolant temperature

Besides those, there are a large number of "indicators" which may or may not be "active"...  After a bunch of research in the electrical manual, those indicators are:

• Check Engine
• Air Suspension Warning
• Washer Fluid Low Warning
• Door Ajar Warning
• Oil Pressure Warning
• Seat Belt Warning
• Air Bag Warning
• Anti-Lock Brake Indicator
• Brake Warning
• Charge Status Warning
• High Beam Indicator
• Left and Right turn signal indicators

And additionally there is the odometer-related data:

• Total Odometer
• Trip Odometer

Getting all that would replicate the functionality of the current dashboard display.  BUT... it would be nice to have some more information beyond these things.  In particular, after more research I think there is a good chance that I can at LEAST get access to enough data to display:

• Engine RPM
• Fuel Consumption (Miles per Gallon)
• Battery + Alternator voltages

 AND, beyond these things, it would be nice to include stuff that modern cars either do or should integrate into their dashboard systems:

• Map display and step-by-step driving directions
• Control of music system
• Maintenance reminders
• Views from onboard cameras (e.g. a "backup" camera to help with parking)
• Other "network" related things like integrated telephone, and "headline" feeds of news items, incoming emails, tweets, and so forth

That adds up to a pretty ambitious set of things, so it is more of a wish list than anything else, but it's nice to know where one is headed when planning a project!