This is actually what happened a few years back when there was a alt-coin called Raiblocks. Right now I think its called Nano. It was basically proof of human and you had to solve captcha puzzles to earn coins. It was similar to proof of work but instead of an ASIC doing the work, it had to be an actual human.

The coin finally hit some exchanges and all of a sudden the Captcha solver services all went up in value and there actually was a way to earn a living doing it 16 hours a day if you lived in some 3rd world country, however there was some abuse going on and it was delisted from Cryptopia and the prices again fell.