Evan Schuman's StorefrontBacktalk

And all the new transaction magic would be going on in parallel with the existing (and untouched) POS software. Mobile coupons, expanded loyalty card offers and even promotions flashed on digital signage at checkout time could conceivably be added to a checkout lane in minutes and removed as quickly.

That’s a lot more nimble than anyone expects Wal-Mart to be. It has been easy to discount things like the iPhone shopping app that Wal-Mart released last week. It’s nice that the app can use barcodes or voice recognition to add items to a shopping list. A year ago that would have been impressive. But a month after the arrival of the latest iPhone—complete with its voice-activated know-it-all, Siri—the Wal-Mart app just seems me-too.

But the ability to do plug-and-play POS experiments falls into a completely different category. By tapping into the POS transaction stream for individual POS units, Wal-Mart should be able to test new checkout concepts very quickly and without touching critical systems. That could mean a lot more low-risk attempts at throwing something new at Wal-Mart customers at the checkout—quick to set up, quick to throw away if things don’t work out.

The Grabble hardware might also enable some store-management experimenting. Which end of the line of checkout lanes are customers most likely to hit, and with which types of products? Do those front-and-back express lanes attract customers with different types of items? Never mind filtering huge quantities of transactions from the existing systems—just slap in a few Grabble boxes to sample what’s moving through key lanes. A day or two later the boxes could be shifted to different lanes—or a different store.

That ability to sample POS data in real time, and experiment with checkout on the spot, is about as far from me-too as Wal-Mart could get.

Will Wal-Mart actually leverage what the Grabble garage-experimenters were working on? Wal-Mart isn’t saying—but that in itself says a lot. There’s a reason the Walmart Labs E-Commerce R&D group is half a continent away from Bentonville. Bringing startups in-house and turning their products into things the chain can get into place quickly, cheaply and with maximum impact isn’t how a behemoth operates. And when it comes to what Grabble can do, someone at Walmart Labs understands very clearly that this isn’t something the chain wants to broadcast at this point, especially to its competition.

Oops.