I got to thinking about the feat toughness, and how it basically lets you treat your character as if they had +2 to their CON score permanently, what if there existed a feat that did the same thing, but let you pick one skill instead, of course there would have to be some steady restrictions on it. Essentially, pick one skill, and you can put a rank into that skill for every hit die you have. Like toughness, you could only take it once, and you would be limited by skills that you can attempt, meaning only class skills and skills that can be used untrained for your character.
Is it broken?
possibly. Skill Focus gives a +3 to any skill (+6 with ten ranks) and is just a feat.