Evan Schuman's StorefrontBacktalk

The biggest practical challenge to in-aisle mobile checkout is verifying the receipt as the customer tries to leave the store. Verification is not foolproof, but it will dramatically slow down traffic, which is counterproductive. What retailers need is a way to associate that phone with the customer and the purchase, and to track all three throughout the store, up to the exit. Fortunately—and simultaneously unfortunately—the very nature of a smartphone provides just such a wireless way.

By using the phone’s signals, the store could track that customer and could know exactly when that customer is approaching the exit and alert the greeter/loss-prevention associate to the approach. No need to verify the receipt, no need to stop the customer at all (unless the greeter sees something beyond the purchased items, but that’s always been the case). There are clearly hurdles to this approach. But it’s one of the few that addresses most of the current in-aisle mobile payment headaches.

As retailers slowly start to experiment with mobile in-aisle checkout (all except Apple stores, which have been doing it for years, the big showoffs), they are having to figure out a way to securely complete the process. One Florida retailer, an NCR beta site, learned about those limits when the store tried to deploy (pay particular attention to the NCR exec’s description of alternative ways to check out securely).

A greeter could scan the image’s barcode and compare it against store records to verify, but that’s going to dramatically slow down store departures. In short, mobile payment’s key attraction is making purchases faster and easier and avoiding lines. Seems silly to just move the bottleneck to the exits.

Even that wouldn’t necessarily work, because a thief—standing by with the bogus digital receipt for the desired product—could just watch that aisle and wait for someone to legitimately purchase that product. Then the thief makes a beeline for the door and a quick scan seems to authenticate the purchase. (“We really did sell one of those SKUs on a mobile phone three minutes ago in aisle 12, just like the customer said.”)

That’s where the phone’s signals come in. Because the phone is frequently sending out a unique (but anonymous) ID to let cell towers know where it is, that signal can be tracked inside a store—through in-store mobile purchases and right up until the customer is ready to leave the store.

The advantage of this wireless tracking approach is speed and convenience, which are the key attributes of mobile payment in-aisle. And that extra CRM data obtained while seeing what that customer does throughout the store is a nice touch.

The disadvantages are also plentiful. For starters, the laws surrounding the use of this information are still developing. As StorefrontBacktalk Legal Columnist—and former federal prosecutor—Mark Rasch argues in his column this week, many types of wireless tracking—even done anonymously and aggregated—may violate federal law in the U.S.

But those laws were written with a very different scenario in mind. If this tracking is limited to making sure that products are not stolen, it might indeed be considered permissible. Some malls in Australia and the UK have been experimenting with such tracking, and the company that is running those trials sees the issues as quite subject to debate.

Another concern speaks to consumers who shop with their mobile phone in airplane mode, effectively transmitting no signals at all.