Long-Term Experiences with an Iterative Design of a QR-Code-Based Payment System for Beverages

We report on the design and long-term use of a digital tracking system for the consumption and payment tracing of beverages, called “Barkeeper”. It is based on tags wearing QR-codes and its design was not primarily guided by efficiency, but rather everyday use during the last three years in our lab. In this trusted environment, we collected extensive usage data, making this a serious long-term field deployment of UbiComp technology. We present the system, its iterative design evolution, the users’ views on it and insights gained by daily usage. We argue that QR-code interaction, when implemented in a very pragmatic way, can be not only a cheap but also a very powerful interaction technique. Based on our experience we propose a set of general rules, which make QR-code-based interaction practical and often superior to other interaction techniques.