Ask the person to turn their head left and right. Or to put on glasses. Combine simple tests like this and it becomes exponentially more complex for the gadget to pass them.
Like the Turing Test computational attack from Rick and Morty.
Rick speaking to a crowd of hologram characters:
Everyone who's first name starts with an "L" who isn't Hispanic, walk in a circle the same number of times as the square root of your age times ten! - https://www.imdb.com/title/tt3333830/
Rick speaking to a crowd of hologram characters: Everyone who's first name starts with an "L" who isn't Hispanic, walk in a circle the same number of times as the square root of your age times ten! - https://www.imdb.com/title/tt3333830/