Sorry guys, it's not just one box; your OBD-II system (all all cars and light trucks made since 1996, records all kinds of drivetrain-related data for emissions compliance; you supplemental restraint system records a continuous loop of data right up until an air bag deploys, and other vehicle systems also keep tabs on various vehicle parameters.
yes, but you can't just unplug the thing. either the car will not run, or the airbag lights will be permanently lit, or some sensor will go nuts, etc.
OBD III is the really scary one. Anyone who is curious can Google it.
Imagine getting an "ecology" ticket because your check engine light is on. A sensor on the side of the road detects it (ecause it broadcasts everything, including your speed) as you drive by and you will get a ticket in the mail.