Pop quiz: A busy mom whips her minivan into a Walmart parking lot. The kids are in the back, buzzing on sugar highs. It’s hot, and mom starts sweating as she searches for her shopping list. Just then, a chime alerts her to an urgent message from Walmart! Question: What should it say? What offer or bit of information would mom possibly welcome at that moment? That, in effect, is the challenge facing Walmart and other retailers with the power to send out location-based, mobile messages, but who don’t know what to say. Brian Monohan, Walmart.com Vice President of Marketing, admitted as much on a panel at Media Magazine’s “The Future of Media” Forum, on Wednesday morning. “What message would [a consumer] want at that momemt?” Monohan asked. More broadly, Walmart is hard at work on improving its existing brick-and-mortar business with digital services. “The world doesn’t need another Amazon,” Monohan said. In other words, rather than e-commerce, Walmart is focused on “e-enhanced commerce,” as Monohan put it.