Phone usage in the classroom has been linked to worsened academic outcomes. We present findings from a field experiment conducted at a large public university in partnership with an app marketed as a soft commitment device that provides incentives to reduce phone use in the classroom. We find that app usage led to improvements in classroom focus, attendance, and overall academic satisfaction. Analysis of time spent outside the classroom suggests a potential substitution effect: students using the app allocated less time to study, particularly on campus. Overall, though statistically insignificant, we find improvements in transcript grades associated with app usage. [This research was conducted in partnership with Pocket Points.]