This was a fun idea that one of my friends had to utilize within my own streams. Basically each viewer would get a randomly generated bingo board and would insert it into their webpage to populate their board. The streamer then would toggle the status of various different "events" they've setup, which would update on every board. Once a viewer got a bingo, they'd let the streamer know and they'd get whatever reward was setup beforehand.
Overall it's a pretty good system. It worked well for my usage of it, people seemed to have fun participating with it! It went well enough that a friend of mine reached out and asked if he could use it for his stream. There's a couple improvements that could be made, like a better way to generate codes for viewers and mobile viewing, but I'll cross those bridges whenever I revisit this project.