I really don't know how to make the script but the logic seems to be possible, any companion with "this ability" activates on;
Player IsSneaking == "this ability" 1
Player IsNotSneaking == "this ability" 0
The second part, don't think it would work if "this ability" is a Constant Ability since it would always be on, what about as Cast Once?
Thanks for any tips or help.