Evan Schuman's StorefrontBacktalk

But Macy’s clearly wants iPhone-carrying customers to try the Herald Square navigation feature—it could have hidden the feature in its app, but it hasn’t. Why won’t it say more? Probably because, even without promotion, this will get a monumental stress test on Thanksgiving and Black Friday. Why risk a high-profile failure?

After all, this location experiment is not a high-stakes gamble for Macy’s. It’s a nice feature to have, but it’s technically complicated, so it’s likely to fail at least here and there. You want to be able to test just the navigation feature and not marry it to something you’re depending on to boost revenue, even though that’s the next logical step with in-store navigation.

The right app features to promote are the less-interesting (such as shopping lists that automatically gin up department name and floor for each item) but more likely to generate Black Friday sales. That’s what those eBay features do. The ideas and technology aren’t new. They’re low risk and high benefit.

That said, Black Friday is still a once-a-year opportunity to test Wi-Fi-based location under the worst possible conditions. Customers and associates will be hitting Wi-Fi harder than on any other day of the year. The likelihood is high for signal conflicts and other glitches that affect the location system.

And if those glitches cause problems? It probably won’t matter much. Customers trying the app will be doing it as a novelty, because no one goes to a major chain on Black Friday just to try out new technology. (Well, no one who’s sane—and if they’re not sane, they’ll fit right in with the Black Friday crowd.)

Those very nice turn-by-turn directions will probably be subject to the same problems a car’s GPS suffers from. If there’s a Black Friday traffic jam in Toys or Electronics, turn-by-turn may be useless. That will probably frustrate some shoppers, but they were going to be frustrated anyway. And it’s not likely that Macy’s will try to augment the turn-by-turn logic with real-time traffic updates for the best route through the planogram.

The location system may not even work at all under the load of a huge number of shoppers’ phones, some of which may be set up to act as Wi-Fi hotspots. There are only so many Wi-Fi channels to go around, many of which overlap, and that could create interference that renders location impossible. (That’s still likely to create less interference than a store full of noisy Black Friday shoppers would for a location system that uses sound-based triangulation.)

If Macy’s new location system works flawlessly on Black Friday, that’s nice, but it won’t do much for sales—at least not this year. If it fails—OK, when it fails—that’s all that fails, and Macy’s and the vendor have time to figure out what went wrong.

There’s also plenty of time after that to develop new features, like having the app report the pinpointed customer location back to a CRM system, so the customer can get real-time offers along with the real-time navigation.

That makes Black Friday something like the perfect testbed—as long as you keep your mouth shut about it. There’ll be plenty of time to talk up your in-store answer to GPS next year.