Customer reviews and recommendations for products are provided by almost all e-business platforms, supporting consumers when shopping on the web. Mobile and ubiquitous computing provide extended means to sense input data for recommendations and to make recommendations available for consumers when shopping in traditional stores. This work contributes a comprehensive design space that outlines design options for product recommendation systems using mobile and ubiquitous technologies. A visual notation for the design space is proposed, based on which existing systems are categorized. Blank spaces are identified and concrete possible extensions are proposed by the example of an existing mobile product recommendation system. Finally, general options for future research on product recommendation systems using UbiComp technologies are discussed.