Is there even another project except gems and effect.ai? I would be extremely interested, these projects could become massive.
Yes I think these 2 are the main ones, effect.ai being more ambitious with the marketplace and decentralized AI.
Stanfords Crowd Research Collective is working on a self-governed crowdsourcing marketplace -Daemo- which could be a competing platform. It's also more user friendly. There are literally millions of people who would be interested in such work, although AI and machine learning is advancing at a rapid pace I think these project if developed properly will have great success.