Geofencing

Card Case from Square sounds interesting. Esentially it lets you set up a "tab" with any store that uses it and they'll just "put it on your tab" when you go up to pay. More interesting to me, though, is the iPhone technology they're using to do it (which I didn't know about): "Square has taken advantage of a new Apple technology called 'geofencing,' which notifies an app when a phone has entered a specified geographical area. The key thing about this approach is that it happens in the background; the app doesn’t have to be on for it to work." As am aside, I've heard rumors that Facebook looks at who else opens the FB app in your vicinity and uses that to recommend new friends.