There isnt a ruling on this, so i'm gonna go by pure logic of how the cards are worded...
Unown H doesnt specify which type of pokemon you can attach it to, so it must include everything.
But, by reading Curse Powder above where it says "Attach CP to 1 of your evolved Pokemon (excluding Pokemon-ex)..." Therefore you cannot attach Tools which state that to Ex's.
The reason why it says "If the Pokemon CP is attached to is a Basic pokemon or a Pokemon-ex, discard CP." Now that isnt saying that you can attach it to Basics and Ex's, since the 1st part of the text clearly says you cant. This part means that if a Pokemon was Evolved/Devolved into an Ex/basic THEN you must discard CP.
I would say that Unown H's attack will Not work on Ex's, because the Tools specifically say 'Excluding Pokemon-ex'. That's the logic of how I see it.