«The kender has a pair of glasses he says are ‹magical glasses of true seeing.› He put them on and he has been able to read the book.»
«Dragonlance Chronicles» by Margaret Weis and Tracy Hickman
Yup, there are already apps, but still, a good idea for an app: AR for virtual graffiti and warchalking.
Virtual Graffiti is pretty clear — you can leave photos, drawings, whatever, in public places, with only the users of the app to be able to see them. Always wanted to paint on a house wall — that would be the chance. You could even make it visible only for subgroups of app users. Or require passwords. Or show different images at different times. Want a Gate to Moria that is only visible in the moonlight when you speak a certain phrase — no problem. Well, the Outline is easy, the door could be harder 😉
Warchalking was something that was used in the beginning of publicly available hotspots (never seen it, only heard about it). Just use chalk to mark where wifi was available (incl. whether it’s protected). A bit like beggar or thief signs. Doing it in AR, much easier.
But why the effort, why AR? You could to the same with a simple maps app. Or heck, with a simple notification.
Yeah, but first, where would be the fun. Having a magical lens with which you can see invisible images or signs … yeah, there’s something to it. But also because you have to be at the place itself. Yeah, you can fake it, depending on the app, you might give false GPS coordinates, or show a photo of the place, or both, but it would be possible. It would be more fun, though, to be at the place itself. A bit like intangible geocaching.
Just an idea. And like I said, not the first one who had it.