Professional baseball always has close umpire judgments. In fact, so do many sports and sometimes, the decision can leave a sour aftertaste. Umpiring by video has yet to be adopted for baseball and soccer but has been used for sumo since 1969. More recently, the International Tennis Federation adopted video replays as evidence in October 2005.
To get back on topic: Sony's VTR PV-100 was the first "portable" VTR and was the predecessor to the video replays. The PV-100 was launched in September 1962 and was manufactured to order. The price was 2.5 million yen. It was 50 times smaller in terms of volume than existing broadcasting models and weighed just 60kg - ideal for taking to competition grounds. It also boasted a slow-motion replay function and was expected to be used for, amongst other purposes, assisting referee calls in sports. After the launch, it was used primarily at sports events, as expected.