Smartphones, as one of the fastest-growing technologies, are quickly becoming a ubiquitous part of our daily lives due to their portability and affordability. One explanation for this is the varied features and functionalities such as web browsing, playing games, and connecting with one's folks through social media and messaging. Despite positive features, smartphones are a major source of task-switching and habitual usage, negatively related to users' working memory, cognitive ability, and learning outcomes. This mixed-method research investigates the role of extrinsic rewards in regulating in-class smartphone engagement, quantifies the impact of smartphone visibility, and explores motivations behind smartphone engagement among university students. Results indicate the motivational model of self-regulation training as a promising approach to addressing in-class smartphone engagement. Smartphone visibility had a significant impact on student learning outcomes. Students reported boredom, availability, and consequences as the primary motivations for engaging with smartphones while in class or studying.