I never thought of ETE as useful, but I guess it can't be unless you have speed limit data to play with.

GPS protocol is only static if you assume most things speak NMEA (which may well be true)

Otherwise, I could see 2 cars having different receiver models.

And as to meters/miles, i think it's one of those deals where if you have more than one driver and one empeg a quick way to change is probably useful. In one car I can deal with meters since the speedometer has km/h calibration; The other does not, so it's harder to think that way.