One of the more demanding tasks faced by teacher educators and mentors is providing high-quality feedback for preservice students during their professional learning. The limited formative assessment currently available impacts on their professional learning. This paper reports on research into how iPhones® have been used by preservice students, supervising teachers and teacher educators to provide formative assessment to preservice teachers on practicum. A purpose-built website and iPhone® application manage communication between preservice teachers, school supervisors, university academics and the university's professional experience unit. The app links captured images, video and written data with assessment criteria. Data from an action research project showed improvement of practicum experiences for mentors and preservice teachers. Results indicate that there is strong support for the use of mobile devices as a means to support supervising teachers in their decision-making processes. Importantly, preservice teachers have welcomed the opportunity to receive powerful visual feedback as part of an on-going formative feedback process.