What I find particularly interesting about it is the potential to produce genuinely relevant advertising. As a simple example, imagine I ask my smartphone where I can find the nearest fast food joint and it tells me there is a McDonald's around the corner. It might also serve an ad that says there is a Burger King one block further away and if I go there and show the ad I will get free fries and a drink with my sandwich.
There are some very interesting possibilities here that we have only begun to scratch the surface of.