What app can you not believe someone hasn’t made yet?
Locations with varying amounts of historical significance are all over the world. Some people are already engaged in geocaching as a hobby and augmented reality games such as Pokémon GO are popular. Why not have an app that can use location to determine if you are in an area with a historical significance and plays an augmented reality view only when you are in the location?
School children will sometimes go to a historical site such as a famous battlefield. Such a mobile app would help "bring history alive" and since the augmented reality of a battle scene for that battle will only work on the app when the phone is located within range of the battlefield it is similar to a geocache treasure. Such an app would also be fun to use when visiting a new city. Maybe the app would have a menu selection for users who want to be morbid and visit famous crime sites involving murder. Maybe a user wants to stand in the Las Vegas desert and watch an augment reality scene of a mushroom cloud from a 1962 atomic bomb test. Who am I to judge what historical events users of the app are interested in?