CrowdCafe - Mobile Crowdsourcing Platform
  In this paper we present a mobile crowdsourcing platform CrowdCafe, where people can perform microtasks using their smartphones while they ride a bus, travel by train, stand in a queue or wait for an appointment. These microtasks are executed in exchange for rewards provided by local stores, such as coffee, desserts and bus tickets. We present the concept, the implementation and the evaluation by conducting a study with 52 participants, having 1108 tasks completed. 
Pavel Kucherbaev, Azad Abad, Stefano Tranquillini, Florian Daniel,   Maurizio Marchese, Fabio Casati
cs.HC