Mobile apps could be fertile ground for researchers seeking new ways to gather data. A team at Northwestern University has tested an Android app designed around the principle of "soft control" — namely, nudging users into performing useful tasks. Their example app, Ghost Hunter, is an augmented reality game that collects photo data of a given location by plotting virtual ghosts on a map and having users "shoot" them with their phone's camera.

It's based around the fact that while a lot of people may take pictures of a certain place by themselves, the resulting set of images is unlikely to cover all bases. In the picture above, the red X marks represent the location of Flickr photos, while the white dots show places where Ghost Hunter users were "soft-controlled" into taking pictures. The upshot is a more comprehensive, crowdsourced data set that could prove more useful in creating things like 3D models. Of course, any app operating like this would need to be completely open about what it was doing with the user's data.

In many ways, "soft control" is a logical extension of apps like Foursquare which rely on voluntary uploads from users, but the use cases are a lot more specific. Aside from image collection, another example scenario is tracking noise pollution in a given area. These may be fairly limited data points, not to mention opportunities for interesting gameplay, but in certain situations it sounds like mobile apps could provide a fun means to a worthwhile end.