Review of unconventional user interfaces for emotional communication between long-distance partners

New form factors and user interfaces for computer-mediated communication are emerging. The possibilities to use these systems for emotional communication are interesting, and recent years have witnessed the appearance of a versatile range of prototypes. In this paper, we present the results of a systematic literature review on research addressing the design of systems with unconventional user interfaces for emotional communication, focusing on the use case of facilitating long-distance relationships. We reviewed a body of 150 papers resulting from a systematic search, further analysis scoping the body to 47 papers, containing altogether 52 prototypes that were relevant for our focus. We then analysed the characteristics affecting the interaction mediated by these systems and their user interfaces. We present the results related to the design attributes, e.g., form factors, modalities, and message types of the systems, as well as to the evaluation approaches. As salient findings, touch input and visual output are the most common interaction modalities in these systems, and their evaluations lack in-the-wild studies, especially on long-term usage.