Yep, although a tracker can dramatically reduce your premium, you must behave! My brother's boss' son just had his insurance cancelled by the company that issued it to him, as they tracked him travelling at 90 MPH. Made it worse by ringing his Dad to tell him too. Lesson learnt!
I used a tracker for a while, under a free trial offer. The insurance company explained that by no means would this device NEGATIVELY affect your policy or premium. Even if you drove around like a hooligan all the time, the net effect would just be no change in your premium. They were looking for extra-safe drivers, and would reduce premiums for them.
Those in the US are only looking at time of day and acceleration/deceleration rates. You have to drive like the EPA test cycle in order to not accelerate too fast.
With mine, the main metrics were time of day, speed, geographical location (some portions of the city are more likely to involve accidents than others), acceleration rates, braking rates, number of left turns (right turns are preferred, so if you make more of those, you get benefits).
Right turns are more economical, Mythbusters proved it .
If you are a delivery driver in a City environment, planning your right to use more right turns than left turns reduces your fuel consumption and I would assume reduces your time on the road as well, due to the lower amount of time you have to wait to turn.
Obviously the reverse applies if you drive on the Left!