The internet raises challenges for retailers, since it provides a competing sales channel that allows effectively unlimited access to arbitrary products. In particular, this enables a phenomenon known as showrooming, where customers inspect products in local stores and subsequently order from arbitrary online shops. By combining large public displays in stores with personal mobile devices, our prototype multiuser shopping system has the potential to alleviate this: Store-specific shopping carts on the mobile bind customers even after they have exited the store. Significantly, the system is optimized to minimize attention switches between the devices by treating the mobile device as eyes-free remote control wherever possible, using the mobile display only for personal data. We report on interaction concepts, our prototypical implementation, and user feedback, contributing an initial iteration for best practices in this domain.