Referred to by most truck drivers as "tattletales", at least that's the PG version of what they were called. We still had them in our trucks when I first started with SSHE.
Now obsolete because of all of the computers in trucks. Our fleet manager can plug in a little device that looks like thumb drive while the truck is being serviced and access all of the complete history of the unit. Speeds, braking, "hard" braking, missed shifts, engine overspeed, fuel consumption, all pressures and temperatures, you name it it's all there, dates times and when coordinated with QualCom records..places.
Damn it, they sure are taking all the fun out of driving anymore!!!