[TeMPOraL]

It's actually pretty simple - don't use it on people.

Advertising? No. Sales? Definitely no.

Augmenting that single-player video game so that it adjusts content depending on emotions and gaze of the player? Ok. Better if the player is explicitly told the game will track their reactions though.

EDIT:

Also, another angle. Even for advertisers / "sales optimization", I'd forgive you if that was a local, on-site system. But if it's meant as a SaaS, with deployments connected to vendor's butt, then I am gonna actively try to screw with it if I learn there's one installed anywhere I frequent. Hopefully new EU laws will curb that, though.

[fixermark]

Editing note: unless it was intentional, you appear to have your "cloud to butt" web extension enabled. ;)

[TeMPOraL]

I had it on for so long that, for my brain, the two words are basically the same now :). I keep forgetting about it when I edit a post (the substitution happens on display, not on submit).

[spuz]

I'm not sure what you mean by your last paragraph. How would facial recognition apply to SaaS products?

[TeMPOraL]

The usual way - many shops buying a "face recognition advertising service" from a single provider, who gets to aggregate all the data.