In my post on the increasing role of technology in helping adjudicate close decisions in cricket, I mentioned three of them: the Hawkeye ball tracker (using multiple camera angles to track the path of the ball and predict its future trajectory), the Snickometer (that displays sound as an oscilloscope signal to show the sound if the ball struck anything), and the Hot Spot (that uses infra-red cameras to detect the minute amounts of heat generated when the ball strikes the bat or the person of the batsman).
The International Cricket Council has decided to not use the Hot Spot for the World Cup games, for purely practical reasons of cost and difficulty in getting enough devices installed in all fourteen of the venues where the games are being played. Thus to ensure consistency they will not use it at all.
The Hot Spot comes in useful in determining if the ball hit the bat in those cases where contact might have been too slight to be visible to the naked eye or the cameras. If the Snickometer and the Hot Spot both indicate contact at the same time as the cameras show the ball at the point of contact, that usually means an unambiguous verdict. Now just sound and visuals will have to do the job.
The question of whether you should not use Hot Spot anywhere because you cannot use it everywhere is an interesting one. Arguing for consistency is easier to make because it seems to equate with fairness. But why is it unfair if some venues don’t have that technology? Venues differ on all manner of things. The pitches are different and the weather and wind patterns and umpires all differ. As long as the differences don’t sway the outcome in one particular direction, it should not matter if some venues use Hot Spot and others don’t.