How's that work with being undead? Since you don't have a Con score, you're not able to take Con damage, and the feat is very specific that its effects are based on the Con damage you take.
Alternatively, I could point out that obscure rule I found when I was digging for things for the Iron Siege where you use Cha whenever a special ability requires Con, which applies in this case IIRC... which I can no longer find. Shit, that was pretty key for any undead challengers, too.