Now FIFA, the sport's world governing body, has announced that it is to test the nine best candidates to see which (if any) could be in place in time for the World Cup in 2014 in Brazil, according to the Associated Press.
However, the demands placed by FIFA on the candidate technologies - which have not been named but are all based in Europe - are pretty onerous. The referee must know within a second what the verdict is, either with a vibration or visual signal sent to something he wears on his wrist. Crucially, the verdict must be 100 per cent accurate, a condition that current systems have so far found difficult to meet.
The two main technologies involved include vision-based system like Hawk-Eye - already used in cricket and tennis at the highest level - which uses six high-speed video cameras to track the ball's flightpath. A second approach is to install a microchip in the ball which senses a magnetic field as it crosses the goal line, sending a signal to the referee.
The last series of tests in March were rather underwhelming: none of the nine technologies tested at Swiss Federal Institute for Materials Research managed to reach FIFA's required benchmarks. The new tests, at the same location, will take place between September and December this year.
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