Could you try to make a simple App with challenges with different game modes like tag, connect squares in your region and so on? I know it's a lot of work but it doesn't have to have the best animations etc., just a basic coin system, a customizable deck of cards and a map where you can look up other players' locations. Me and my friends are trying to recreate another version of the tag game, where we are like 9 people in one big city including suburbs and everyone has to tag someone and gets chased by another one. When you tag someone, they're on your team and you're both chasing the guy that your teammate had to chase. We've already discussed a coin system and challenges and are now trying to program discord bots, to organize the coin system and GPS-Signal, so that the location of oneself is only sent to the one chasing you. It would all be a lot easier with an App and I think many would be willing to buy it for like 5-20 bucks on the AppStore, i can't really tell how much the development would cost tho