In general, a scrutineer is a person who observes any process which requires rigorous oversight, either to prevent the occurrence of corruption or genuine mistakes. It is most commonly known as part of voting in an election, where the scrutineer observes the counting of ballot papers, in order to check that election rules are followed. There are other uses of the concept, such as in motorsport, when a scrutineer is responsible for ensuring that vehicles meet the technical regulations.
Rules vary concerning the number of scrutineers that are allowed to be present at each polling station from a political party. In some jurisdictions, each candidate or party may have one scrutineer or poll-watcher per constituency or precinct where voting or counting is taking place. In other jurisdictions, such as Australia and Canada, each party is permitted to appoint one scrutineer per ballot box. They are often required to refrain from contact with voters, wearing or displaying political slogans, or otherwise exerting influence on the conduct of the election while it is taking place.
Scrutineers play an important role in many motor sports. Racing series typically have a set of technical regulations to which the cars, bikes or other vehicles must conform. The role of the scrutineer in this case is to confirm that vehicles entered for the race meet the relevant regulations.
Someone who carefully verifies the accuracy of Technical Specifications, Drawings, or Configurations as they apply to a specific discipline field.
Competitive Dance 
Dancing competitions (especially Dancesport) employ (usually professionally certified) officials who oversee judging and tabulates scores. Software is often used to aid with tabulation. Two popular platforms are CompMngr and O2CM. In the UK there are a couple of popular applications for Scrutineering dance competitions. One that is used at most prestige events is Scutelle Easycomp is another option
The names Poll-watcher and Challenger is commonly used for this role in the United States.