When standing within your area of influence, CNPC allies always ignore how wounded they are when you attempt to control them in combat.
E.g.: Ted and Destructo are fighting deathclaws. Destructo's got nothing against deathclaws, but he isn't too fond of the gaping wound that's left him with 28/100 hit points. Normally, he would head for the hills, even if his enemy was pretty wounded. However, Ted's a Suicide King, so Destructo knows that his pal will get him out of this mess somehow if he just follows his lead. (i.e., Destructo ignores his wounds for purposes of comparsion to Ted's Persuasion). Ted exercises manual control over Destructo. He has him attack the deathclaw, killing it, then has Destructo move down next to Ted. On Ted's next turn, Ted uses a Super Stim on Destructo, and everyone is happy until the other three deathclaws get in melee range.
The perk description was posted by J.E. Sawyer on the Interplay forum in 2003.