Duel Gazer

A Duel Gazer, known as a D-Gazer is a device in the ''Yu-Gi-Oh! Battle Realms'' universe which is worn over a person's eye. It allows the wearer to see in augmented reality.

They can be used as communication devices, much like a telephone but they also allow video calls. They can also connect together or Duels and allow any other Duel Gazers to link to the Duel to see it. This most likely allows spectators to follow just one Duel even if there are multiple Duels using Augmented Reality occurring in the local area. They can also be used to check set cards if a player forgets what card they set and its effect.

The Duel Gazer has a standard version but most customize theirs.

Supernatural Duel Gazer
Some characters like the Guardians of the Night or Raven Doomsday don't need a Duel Gazer instead their eye glows and allows them to see augmented reality. These people all have a connection to some sort of supernatural power and are mainly the antagonists of the series.