[aero142]

It's better with this than with a CC. You get a notification on your phone immediately, so they are likely to get caught at the moment they do it. You could walk up to the manager and say, "Hey, someone just charged me for something I didn't order. With a credit card, they might take the credit card nimber when you buy something legitimately and then skim it and use it later. It's hard to know which time you used the card and it was skimmed and who purchased something later. This sounds more secure.

[6ren]

Nice point. A notification just-after is almost as good as authorization just-before.

An exception I see is that it works even when your phone is off, so you wouldn't be aware of the notification (or so I assume - do some phones buzz/beep, even when off?) Of course, it makes it riskier for a malicious cashier. I suppose they could check who has their phone off first, but the risk is certainly mitigated.