The Integrated Diver Display Mask (IDDM) is a diving mask which contains a small basic heads-up display that lets divers monitor depth, bottom time, tank pressures, and related information while leaving their hands free for other tasks.
Oceanic / Aeris supply it. It was developed by Oceanic and the U.S. Navy. The United States military has adopted it.
References
Integrated Diver Display Mask Wikipedia(Text) CC BY-SA