We've had trackers for years.
Around 200 company vehicles and most have them, those that don't are short term hire awaiting replacement, like mine at the moment.

In 8 hours you must have at least a half hour break.

Driving time doesn't count in working hours, at the moment.

Ours were fitted originally because some of the fridge service engineers we had were definitely taking the piss.
Most of those left at the mention of tracker.

One guy we have at the moment is given a weekly tracker report to make sure his time sheet matches.
He is forever forgetting to book O-T and looses money without tracker.

.