If you were to use a Rebuke Technology spell upon a humanoid who possesses a cybernetic augmentation, what would happen?
If it isn't affected by default, could an opponent target the limb or (in some cases) cybernetic brain?
If they could... what would occur?
You can't target a non-technological creature with rebuke technology, but you could target the implant itself provided it's visible. That would render the implant inert unless the creature made its saving throw.
Targeting an implanted brain would usually be impossible as you wouldn't have line of effect. If you do somehow have line of effect (maybe it's a clumsy implant that leaves itself exposed to the air), it'd disable the brain, which would either render the creature unconscious for the spell's duration, kill the creature, or possibly nothing, at the GM's discretion.
Are implanted brains even a thing? You usually need to have a brain to receive implants, and all I see on Ye Thirde Partie Syte are a few brain slot chips that would simply cease functioning.
/insert head of vecna joke here
There is a brain slot, and you can replace some of your brain. The skillslot is Paizo's primary example. Dreamscarred Press has cybernetics to replace larger portions, but that is third party.
Here's an example. You can replace your eyes with cybernetic eyes. Does that mean that forever you can be struck with spells that simply turn off your eyes?
Yeah, pretty much. They get a saving throw, after all, and blinding someone permanently is a level 2 wizard spell already, so it's not exactly crazy.
The skillslot is what I was looking at--rebuking that would just disable the slot and any skill boost associated with it. The rest of the brain shoild work fine.