  Most mobile health apps employ data visualization to help people view their
health and activity data, but these apps provide limited support for visual
data exploration. Furthermore, despite its huge potential benefits, mobile
visualization research in the personal data context is sparse. This work aims
to empower people to easily navigate and compare their personal health data on
smartphones by enabling flexible time manipulation with speech. We designed and
developed Data@Hand, a mobile app that leverages the synergy of two
complementary modalities: speech and touch. Through an exploratory study with
13 long-term Fitbit users, we examined how multimodal interaction helps
participants explore their own health data. Participants successfully adopted
multimodal interaction (i.e., speech and touch) for convenient and fluid data
exploration. Based on the quantitative and qualitative findings, we discuss
design implications and opportunities with multimodal interaction for better
supporting visual data exploration on mobile devices.
