The growing ubiquity of smartphones offers public transit agencies an opportunity to transform ways to measure, monitor, and manage service performance. We demonstrate the potential in a new tool for actively engaging customers in measuring satisfaction and co-monitoring bus service quality. The pilot initiative adapted a smartphone-based travel survey system, Future Mobility Sensing (FMS), to collect real-time customer feedback and objective operational measurements on specific bus trips. The system uses a combination of GPS, Wi-Fi, Bluetooth, and cellphone accelerometer data to track transit trips, while soliciting users’ feedback on trip experience. While not necessarily intended to replace traditional monitoring channels and processes, these data can complement official performance monitoring through a more customer-centric perspective in relative real-time. The pilot operated publicly for three months on Boston’s Silver Line (SL) bus rapid transit, in collaboration with the Massachusetts Bay Transportation Authority (MBTA). Seventy-six participants completed the entrance survey, half of whom actively participated, completing over 500 questionnaires while on board, at the end of a trip and/or at the end of a day. Participation was biased towards frequent SL users, who were majority White and of higher income. Indicative models of user reported satisfaction reveal some interesting relationships, but the models can be improved by fusing the app-collected data with performance characteristics obtained through the automatic vehicle location system. Broader and more sustained user engagement remains a critical future challenge.