NASA's Kepler, TESS, and Roman missions are providing high precision time-series photometry of millions of stars in the search for transiting planets. While wildly successful at revolutionising our understanding of planetary systems, these data also provide a unique opportunity to study the evolution of magnetic activity across stellar lifetimes. From stellar flares to rotation and brightness variations on years-long timescales, these missions have transformed our understanding of stellar activity and how it varies with stellar mass, age, and composition. In this talk, I will present an overview of how these exoplanet-focussed missions have enabled a lagniappe of science results, improving our understanding of stellar surfaces, and some of the opportunities to extend this understanding further in the coming years.