The fire phone did this 7 years later with 4 front facing tracking cameras and nobody cared
It always seemed gimmicky to me, but I’ve heard that the Mario brothers 3D worked a lot better with the depth element than in any of the remakes (I did it enjoy it just fine on my switch)
It was fun and worked pretty well, but it was very much a gimmick.
EDIT: Just saw the other comment, I didn't know the New 3DS had actual eye tracking. Neat!
I think the original 3ds's lack of tracking is what turned it off for most people, though.
He managed to get a brand new in box one, not spoiling if it works or not you'll have to watch to find out...