In this article, we aim to analyze processes of knowledge production about double integrals using smartphones and GeoGebra with higher education students, through the lens of Activity Theory. As a theoretical framework, we draw on the third generation of Activity Theory (AT) to support the analysis of human activity. For data production, of a qualitative nature, we developed an Undergraduate Teaching Project over the course of five sessions held across three Mondays in November 2019, involving 11 students from Mathematics and Physics programs. Through smartphone screen recordings made by the participants themselves, along with written productions and interviews, we analyzed the videos of one trio and interpreted that the smartphone—through its visual appeal and capacity for instant feedback—has potential to provoke or support transformations in the ways knowledge about double integrals is produced, and to help visualize the extension of integral concepts. The results show that participants expanded their understanding from single to double integrals, albeit with some inaccuracies. The use of smartphones with GeoGebra supported learning through visualization and interaction, though its effectiveness depended on community mediation. Internal tensions within the activity system drove conceptual reconstructions, while technical limitations of the devices were also identified. Overall, knowledge production occurred in a collective and mediated way, confirming the suitability of Activity Theory as an analytical framework.