Have you ever been walking down the street on a hot afternoon and were minding your own business?
Perhaps you look at your phone and you see an add for iced coffee, complete with a coupon.
Looking up, you see that very franchise not thirty paces in front of you.
What. A. Coincidence.
Geofencing uses your phone location to send very targeted messages to your phone.
In this case, the advertiser put up a "fence" on a busy street within line-of-sight of the enterprise he was paid to provide advertising for. The coupon code the customer uses to get $1 off his $6 iced coffee is keyed to the fact that that the geofence routed the customer into the shop.
Geofences can be turned on-and-off. The fence can be turned off when the coffee shop is normally busy and turned on during slow times.
It suggests all kind of potential for mischief to mess with rioter's minds. Examples to follow.