10th man down,
You're mixing up two different items.
An amulet of might fists +x from the DMG gives an enhancement bonus to attacks & damage for all natural/unarmed attacks.
A necklace of natural attacks +x (I think that's what it's called) from SS gives an enhancement bonus to attacks & damage, & can have weapon special abilities, but each natural attack will cost separately.
Additionally, bracers of striking from Magic of Faerun can have weapon special abilities (which cost double the gp), but apply to all natural/unarmed attacks.