Extradimensional jaws...

[VoodistMonk]

I am wanting a breastplate that has a set of jaws that can snap out of it to swallow someone standing in front of the wearer...

Whether or not that exists, it got me thinking about fun ways to get Swallow Whole, or similar abilities. I know about the Tyrant Totem Rage Power(s), but was hoping there was more. I'm not really looking for polymorph effects that transform the character into something else that has Swallow Whole, either.

The reason I ask about extradimensional Swallow Whole in particular, is because I like small races... and I am quite amused by the thought of a Grippli [frog] bulping down their enemies (of which, most are medium, or larger).

A breastplate with dragon jaws that pop out reminds of something... an old video game or anime, perhaps... I cannot place it exactly... it might have been a werewolf that had extra big wolf jaws that busted out of its stomach... I just cannot remember right meow. Anyways, I figured a piece of armor might already exist that has a similar function... maybe a mirrored shield with the magics from the Mirror of Life Trappig... some such $#!+... I am willing to reflavor something if it exists already.

[Pizza Lord]

I don't know of a current Pathfinder option.
I know it reminds me of a 3.X spell, Bite of the King.
It's incredibly high level and rare, since you had to worship a deity of Hunger or one of the seven sins (Gluttony).

Bite of the King:

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Bite of the King
(Spell Compendium, p. 27)

Necromancy
Level: Hunger 8, Gluttony 8,
Components: V,
Casting Time: 1 Standard Action
Range: Touch
Target: One living creature of a size that does not exceed the caster
Duration: 1 round/level
Saving Throw: Fortitude negates
Spell Resistance: Yes

Your mouth opens impossibly wide and engulfs your foe. You swallow loudly and your mouth returns to normal size, leaving no trace of your foe behind.

When you cast this spell, you can send a creature to a pocket "stomach" dimension with a successful melee touch attack. The target you touch must make a successful Fortitude save. If it fails its saving throw, the creature is sent to the stomach dimension. The victim takes 2d8+12 points of bludgeoning damage and 12 points of acid damage per round while in the stomach dimension. The victim can cut its way out by using a light slashing or piercing weapon to deal 35 points of damage to the stomach dimension (AC 21). A creature that successfully exits appears to cut its way free from thin air, appearing in a space adjacent to you.

Each time you cast this spell, you create a separate temporary stomach dimension.
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If you're making such an item, the spell could certainly be used as a template or guideline. Something like a Lion's Shield that adds this ability onto a successful bite attack when used.
Not of specific help, since it doesn't allow bigger targets than the caster, but since it's the shield and not the wielder that casts the spell, it might be possible to increase those parameters. Just some thoughts.

[*Thelith]

Jaws!