In short, we've moved far beyond using regular old GPS for location tracking. Indoor environments are challenging for low-cost location systems such as GPS, because the ways in which buildings are constructed--not to mention physical obstacles and even people's bodies--interfere with GPS's ability to pinpoint a location.

One example of the new technology is the Navizon Indoor Triangulation Service, which MIT's Technology Review blog discussed recently. Location services company Navizon says that ITS can provide accurate tracking of Wi-Fi-enabled devices, including smartphones, tablets, and laptops, anywhere inside a building or throughout a campus. (Triangulation by Wi-Fi hotspots helps to make location services more accurate.)

As such services begin to grow, they might threaten your privacy. So, in many instances, if you don't want an entity knowing the location of your mobile device, you should shut it off or .

At the same time, however, device tracking could become hugely useful to you. Innovators have figured out how to take GPS-like navigation indoors so that people can not only quickly find the restroom in a department store or their departure gate at the airport, but also receive deals and discounts from retailers upon stepping over a shop's threshold.

Navizon wouldn't comment for this article, but some of its competitors did. Let's take a look at other companies working on IPS services.