A free mod for Fallout 4, by BestPJ.
This mod makes it so that the player also goes into a state of bleedout when they lose all their HP. When you lose all your HP, your follower will try to revive you, just like in the vanilla game.
This mod also makes it so that if you have more than one follower, they will try to revive each other when they go down.
The amount of time it takes for them to revive you can be configured on the settings.
Just like in the vanilla game, only one follower can be reviving at a time. The follower is also susceptible to enemy fire.