Given the growing prohibitions and restrictions on cell phones use in schools worldwide, a study addresses student perceptions of the opportunities and threats surrounding smartphone use in experimental and theoretical physics classrooms. Based on a sample of 180 first-year engineering students at one public university (n = 84) and one private university in Chile (n = 96), this study provides more elements for to contribute to the open global discussion on when and how this powerful tool (smartphones and their variety of sensors) can be used for academic purposes. The qualitative and quantitative research results show positive perceptions and consider smartphones a contribution to the classroom. In the case of using the smartphone as an interface in physics laboratories, more than 60% of students from public and private universities says they strongly agree. However, when smartphones are used without blocking applications, social media messages and alerts break student concentration, making refocusing on their academic activities very difficult. That is when smartphones become a distraction, and their potential positive contribution actually begins to be a threat.