Tangential: I wish we had open betting/prediction markets for everything. At the risk of being naive, I had this idea of matching speculators with insurance buy

Tangential: I wish we had open betting/prediction markets for everything. At the risk of being naive, I had this idea of matching speculators with insurance buyers on a platform. Example: If I'm hosting an outdoor event in 2 days and I want to hedge against it raining on that day, I can buy insurance (bet against sunny) and get paid if it rains. Speculators can make money by selling insurance. Sort of like options trading but for real world events. Does this exist? Is it even legal?