The idea is straightforward: Associate a series of ads with a specific individual as well as predetermined GPS coordinates. When those ads are served to a smartphone app, you know where that individual has been… It’s a surprisingly simple technique, and the researchers say you can pull it off for “$1,000 or less.” The relatively low cost means that digitally tracking a target in this manner isn’t just for corporations, governments, or criminal enterprises. Rather, the stalker next door can have a go at it as well… Refusing to click on the popups isn’t enough, as the person being surveilled doesn’t need to do so for this to work — simply being served the advertisements is all it takes.

Source: For Under $1,000, Mobile Ads Can Track Your Location – Slashdot