[benrequena]

Here's an app idea. Show notifications when the device is within a certain distance from the location of a past historical event. ...or past Crime ...or a message another app user has left.

[mikeevans]

Here's a Parse sample app that does something very similar: https://parse.com/anywall

[mtoddh]

I like this idea- it would be cool when exploring a new city if had a preset tour feature where it would guide you through these past historical events, crimes, etc. depending on which theme you chose.

[saraid216]

This smells like an ARG. And even if it isn't, there are plenty of overlapping demographics who'd like it.

I can see all kinds of weird unintended uses for it, too. ("Alice <3 Bob" marked in random places.)

[mapster]

would be a cool bike or car app - your get a notice when you are near a hotspot for bike or auto accidents. Give the user a heads up. Possibly to scrape this data from county GIS sites or police maps.