Awareness

Awareness is a passive skill, unlocked at level 66.

In-game
Cooldown Reduction does not help reduce the 60 seconds recharge period. The debuff is removed, however, if the character actually dies.

For obvious reasons, this skill is considered mandatory for Hardcore characters.

Beckon Sail cloak provides exactly the same effect as this skill, except for its duration and healing are halved compared to Awareness, and the cooldown is doubled. These two methods do not share the cooldown with each other.

Development
Originally this skill was increasing Dodge chance over time (6% per second, resetting 1 second after successfully dodging an attack), in the same manner as Sharpshooter is increasing the Critical Hit chance. As of patch 2.0.5 and until 2.1, it was instead providing the Demon Hunter with a bonus to their Armor equal to  of their Dexterity. This way, the Demon Hunter was the fifth class to gain the "life-saving" passive ability (leaving the  to be the last, as of patch 2.2.0).