Virtual scanner headset

A virtual scanner headset was a virtual sensory display device used by the Dominion which enabled them to see outside the vessel they were on without the need for a viewscreen. Aboard Dominion vessels, only the Jem'Hadar First and the Vorta commander wear the headsets. 

Skrain Dukat used a virtual scanner headset during the Dominion attack on Deep Space 9 at the start of the Dominion War. Three months later, Elim Garak, having seen Dukat wear such a headset, offered to stand in for Benjamin Sisko during the mission to destroy a ketracel-white facility. The headset, which had had given Sisko headaches, was described by Garak as "like having a viewscreen inside your brain". 

Garak would later wear a virtual scanner headset again in 2375. Kira Nerys wore a virtual scanner headset during the mission to obtain a Breen energy dampening weapon from a Jem'Hadar warship docked at the Kelvas repair facility. 

Odo and Weyoun wore virtual scanner headsets aboard Jem'Hadar Attack Vessel 971 in 2376. 

The $𝜇$ of the mirror universe also use the headsets.