Uber riders are a literally captive audience, so it’s no wonder that the ride-sharing giant says that its ad engagement leaves other retail media networks in the dust. But this week TWIRM is asking: Will Uber’s first-of-a-kind “custom metrics” rewrite the rules of the retail media road?

TWIRM, as retail media mavens everywhere know, is the This Week in Retail Media podcast, hosted by Kate Dickson, Head of Marketing and Communications, Retail Media, STRATACACHE, and Jonathan Rosen, STRATACACHE’s Global EVP of Retail Media Strategy. Each week, Kate and Jonathan dive deep into three retail media stories that excite them, intrigue them and even, sometimes, make them “pump” the proverbial brakes.

The top story this week, courtesy of AdExchanger, is about Uber’s launch of its Custom AU platform for Uber Advertising, developed with attention measurement startup Adelaide and brand lift survey provider Kantar. The platform will ditch the IAB’s (admittedly low-bar) standard for ad engagement—50% of pixels visible for one second—in favor of a metric culled from its own first-party ad engagement data, correlated with brand lift data. Notably, this will be the first “custom metric” for a major scaled retail media network.

But it won’t be the last, as competitors are sure to design their own bespoke metrics to woo marketers and brands. Kate wonders how this will impact metric trustworthiness. “If everybody’s got their own version of (metrics) and spins it so it looks like they’re performing particularly well, there’s going to be no base of truth anymore,” she muses.

From pondering Uber’s metric moves, Kate and Jonathan check out U.K. retailer Co-op’s in-store scale-up with its installation of its 1,000th front-of-store digital screen. Lastly, they look at Amazon’s new Whole Foods plan to let shoppers QR-code order national brands from a back-of-house micro-fulfillment center—bringing Coke and Crest to the organic grocery giant.

Click here to listen to Kate and Jonathan discuss whether Uber’s custom metrics will launch a new Wild West in retail media measurement.