Backstory: Julia and I have been playing a lot of trivia lately and we're always looking for a unique/different take on games.
The Idea: A mobile game where a picture of a famous landmark or city pops up and you have 15 seconds to point it it's location on the map.
Deep Dive: You would receive points based on how close you are to the actual lat/long of the landmark. There could be an option to play with friends or strangers, this game could support multiple people depending on technology implementations.
You would have to play with the game mechanics, 15 seconds may be too long. Additionally you could have a set number of rounds where people win based on cumulative points.
Validation: That HQ trivia game is very popular, interactive trivia games are trendy.
Monetization: As this is a mobile app you could have a mobile ad banner and the option to pay to remove.