Wayne Enterprises has always been involved with cutting edge technology. Even more, it allows them to be unconventional; just think of the Batmobile. It's a hybrid between a car and a tank. And then, there's also the other gadgets Batman uses in his missions.
The Batmobile is just one of the many weapons available to the Dark Knight to fight the bad guys across Gotham City. And just as the film came out in 2008, GPS also started to gain popularity and came in service of justice.
While the Joker was out playing his sadistic games, Batman tracks him through the cell phones of various people to build a dense network of links on the map. Basically, he was able to monitor any suspicious activity happening in Gotham City.
The fact that smartphones are powerful monitoring tools is clear to everyone. What may be unclear is that the ability to monitor a person's comings and goings can be a very interesting source of information not only for Batman and (or villains) but also for retail managers.