Is there already an item like this?

[Yqatuba]

Is there a cursed helmet that if someone wears it they have to save or are dominated (by the maker of the helmet) for as long as they wear it? I assume someone could pull the helmet off but it would probably require a steal check.

[PodTrooper]

Nothing comes to mind off top of my head.
It would be easy enough to write up though. A helmet with a permanent Dominate Person effect.

A lot of possibilities also exist, just using the rules for intelligent magic items. A strong enough item could cause some battles for control with the wearer.
And it would probably be a surprise to the players, since for some reason, not many groups use intelligence for magic item, other than for weapons.

[Temperans]

Not exactly what you want but there are a few items with similar feel that you can modify and work around.

The Torc of Kostchtchie, it's an artifact that can make you go berserk the more its use.

Laubo Powder, effectively makes Voodoo zombies.

Ironbound Rings, wearers of the minion ring can't go against a 50 word order given to the ring. At least I think that's how it works.

Marionette Crux, make an attack and the target must save vs dominate, who ever holds the crux has control; If the target holds the crux it ends. So a cursed version might have the person who hold it willingly (wears it if you shape it into a crown) gets dominated by the crafter or some other thing.

Also for the intelligent item, a Ring of Obsession fluffed as a crown with the obsession being "serve the creator" could work really well. The ring gains +10 ego when doing its obsession, so something like, "I wish for you to do this for me, here is X to aid you in your quest", would catch things hook, line and sinker.

[Cevah]

PodTrooper wrote:

Nothing comes to mind off top of my head.

Like that helmet?

I recall the Sihedron Medallion.

/cevah