I have mixed thoughts about trackers...
If the vehicle is going to be completely written off, then yes, a tracker would speed up the process of locating the vehicle and getting your claim sorted, as you wont have to wait for it to be located by the police, or given up on after a few weeks.
If however, the theives take the car and smash it or thrash it to a stage where it is damaged, but repairable - would you want it back? Or would you rather it not be found until you have had your total loss payout?
If my car gets stolen, I dont want it back, as it will be marked as a stolen recovered, and god knows what may have happened to the engine if they have given it some real abuse... If it has a tracker, you stand more chance of getting it back and having to have it repaired and put back on the road.
I've taken out a form of GAP insurace, whereby if my car is a total loss in the first four years, the difference between what the insurance company pays out and the price I paid for the car (the depreciation effectivley) is made up - so if it is stolen I deffinitley dont want it back, as Ill be able to afford a brand new one if it is a total loss.
So swings and roundabouts really. Im not anywhere near as paranoid about the car being stolen as am about it being dented by some ignoramus and their door in a car park.