Smartwatches have become widely adopted for everyday tasks, including activity tracking, notifications, and health monitoring, owing to their portability and ability to capture diverse data. While prior work has shown how smartwatches enrich multi-device systems and improve user experience, we still lack a systematic understanding of their roles, usage scenarios, and evaluation practices within these ecosystems. To
address this gap, we conducted a systematic review of 106 studies on smartwatch-based multi-device systems. These studies were published across six leading Human-Computer Interaction conferences and five top-tier journals, with a cutoff date of November 2025. Our analysis identified two system configurations, seven smartwatch roles, common application contexts, and the evaluation methods employed across
these studies. This work contributes to a clear understanding of how smartwatches function within evolving multi-device systems and offers guidance for future research on the design and integration of multi-device ecosystems