You're not really TRACKED per se. They can get data on speed, gas pedal percentage, brake deceleration, time... that sort of thing, there's no location or directional tracking (they pull that off the GPS).
... but what they are doing may be a little underhanded. We all lie to our insurance applications. Grabbing all this REAL data gives them a new data set to rate us with. We ALL say we don't speed, don't slam on the brakes, only drive to church on Saturdays, whereas the data they're pulling off the ODB says that 75% of the applicants that say that are actually driving like fools.
According to Reddit most people that get that ODB thingee don't get a reduction, some have had their insurance cancelled (which IMMEDIATELY puts you in a higher rate group), and trying to drive in a way you get good "points" isn't easy or safe.
But your phone IS tracking you in realtime, location and direction, even if you turn off the GPS