[stcredzero]

I always wonder if hearing aid has military applications

One of the biggest advantages of German tanks in WWII, was the excellent communications system. It was engineered so that all members of the crew could clearly hear instructions in battlefield conditions.

Technology which can improve communication and perception and also protect hearing in battlefield conditions always has military applications.

Is it possible to have an above average hearing with this?

You can already buy consumer electronic hearing protection devices which can allow you to hear quieter sounds than otherwise, while protecting you from loud transients.