I built a prediction market for the 17th Henryk Wieniawski International Violin Competition. It uses an opening line set by votes from my Duels feature and an AI panel forecast. There are a couple games such as the brackets (pick who advances to the next stage), parlays, as well as group odds. Play points are used, but cash prizes are given away out of my own pocket. The community is divded about the ethics of such a site.