I built https://explorehere.app to help you learn about the history of the world around you by sending a push notification whenever you pass a new historical marker on your travels! It’s a freemium app with a pro subscription for advanced features; our revenue is just under $1k/month. We’re working towards ExploreHere being a passive adventure guide. As you go about your travels ExploreHere will nudge you about interesting information wherever you go; history, unique things to see, special food known only in the city you’re in, etc.