I'm working on a game that helps with this. You leave your little bunker in a post-apocalyptic world and find the land around you contaminated. You walk, run, any workout, to claim territory around you, and gain energy you can use to clean up. You start building greenhouses to grow food and start rebuilding the ecosystem. It's all on the real world map underneath you, and all the interactions between people in the game are cooperative: you get more benefits helping another player with most actions than doing the same thing in your own territory.

The game tricks you into going for walks or runs regularly since you need those energy points for everything, and I'm building out more cooperative behaviors to give you reasons to go walk with someone else, go work together to fight an alien infestation, and more. You'll discover other players in the game who are near you in the physical world, and be able to request help, thank them, give them benefits, all positive.

I've learned a lot from Niantic's strategy, but they've never leaned into actually helping people improve their fitness, or work out together. I'm hoping I can help solve this problem you're talking about, at least for getting people fitter!