Don't Worry, Be Happy - Exploring Users' Emotions During App Usage for Requirements Engineering

User feedback and usage data are a valuable source of knowledge for requirements engineering (RE) and software evolution. Recent research in RE has focused on the acquisition and analysis of such user input. However, we argue that important information complementing existing data has been neglected, namely users' emotions shown during app usage, which provide insight into how users experience the app. We are aware that tracking users' emotions at large-scale might be challenging. So far, emotion tracking is often applied in lab and test settings only. We envision an unobtrusive emotion tracker running on the users' smartphones in their regular usage context. However, we do not know whether such an approach would be accepted by the app users and which requirements such an emotion-tracking solution would need to fulfill. In this paper, we present the first results from our exploratory interview study with eight mobile app users regarding their preferences and concerns with respect to emotion tracking. Early results are encouraging and suggest that app users tend to accept emotion tracking during app usage, having only minor privacy concerns. In this paper, we discuss our ongoing research, including the long-term direction and prospects of considering users' emotions for RE.