If you walk almost anywhere, you will see plaques celebrating and informing you of interesting people and facts regarding many places (buildings, parks, etc.) There are much more of these than you see on these plaques and many a place where there is no plaque even though it has an interesting history.
An augmented reality app that when pointed at such a place gives you a list of all the interesting things that happened. Famous people who lived there, historical events, etc. You just point it at a building or even a few buildings, or a whole park, and see the list pops up on the screen beside the place you point at. You can them click on any of these to get many more details and the story.