A First Step Towards Indoor Navigation. Literally
The problems started the moment GPS became a commodity and made the transition from the car to the mobile device. Nowadays, GPS can be found in a vast range of smartphones and navigation is possible without being confined to your car. Of course, it's not always a great experience. GPS works best when there's a direct line of sight to the satellites whizzing around over your head and there are times when you just can't get a GPS lock. A-GPS was devised to help with such situations, allowing your location enabled to device to take advantage of a variety of other sensors, such as cell tower and wifi triangulation technologies.
But even then, GPS just doesn't work indoors most of the time and indoor location and routing has become something of the Holy Grail for navigation technology vendors. Granted there have been lots of technologies developed which use non A-GPS technologies such as RFID and other near field sensors. But so far these all require a not insignificant investment to install and require specialist devices to take advantage of; none of which are as ubiquitous as the combination of smart phone and GPS.
Maybe we're looking too deeply at this challenge. Take a category of location that lots of people go to, such as shopping malls, where GPS usually isn't available, and map each mall to a high degree of accuracy, both in terms of the layout of the mall and in terms of the stores and concessions in that mall. Add in key features, such as multiple levels, staircases, escalators and lifts and you can build a spatial map of the mall which doesn't need sensors. Simply tell your phone where you are and where you want to go and you can provide simplistic directions, without the need for GPS.