The technology that still works even if cell signals are blocked ( i.e. cell phone jamming ) is Beacon or iBeacon (apple) :
"They are poised to transform how retailers, event organizers, transit systems, enterprises, and educational institutions communicate with people indoors. Consumers might even want to deploy them as part of home automation systems ."
With iBeacons :
"companies will be able to provide deals to people that are walking past their stores. But for now, iBeacon will simply help people that are already inside an Apple retail location." [more]
Payments - Proxima Wallet :
"On the user’s side, there is no physical credit card to take from your wallet; you do everything in the app. On the vendor’s side, there is no card reader that needs to be plugged into your phone; the iPhone itself, as you bought it, is the cash register. No swiping required"
'you’re able to get an approximate range in terms of distance to the beacon,” Nolan says. “So you join the queue to buy something from the vendor and when you get to the top of the queue the vendor can take your order, which is all seamlessly handled by the software the vendor uses. You approve the purchase and the entire communication is handled securely over the multipeer APIs Apple shipped in iOS 7, and proxied through the vendor’s device if your device does not have a currently responsive Internet connection'