  Nowadays, different types of context information are integrated into mobile
messaging to increase expressiveness and awareness, including mobile device
setting, location, activity, and heart rate. Due to low recognition accuracy,
sometimes users cannot accurately infer others' status through activity
awareness. Recently, activity recognition technology has advanced. However, the
user behaviors of activity awareness with improved technology have not been
studied. In this study, we design ActAware, a mobile instant messaging
application that integrates activity awareness based on improved activity
recognition technology, i.e., improved recognition accuracy and the addition of
activity transition notification. We conduct a field study to explore user
behaviors and found that activity awareness allows users to speculate on the
reasons for chat interruption, plan communication, speculate on whether the
chat partner is departing/arriving, and deepen the understanding of living
patterns. Compared with disclosing other types of context information, users
have fewer privacy concerns about disclosing activity information in ActAware.
Based on these findings, we provide design recommendations for mobile messaging
to better support activity awareness.
