High-angular-resolution cosmic microwave background experiments provide a unique opportunity to conduct a survey of time-variable sources at millimeter wavelengths, a population which has primarily been understood through follow-up measurements of  detections in other bands. Here I report and expand on the first results of an astronomical transient survey (https://iopscience.iop.org/article/10.3847/1538-4357/ac06a3) with the South Pole Telescope (SPT) using the SPT-3G camera to observe 1500 square degrees of the southern sky. I will also discuss on-going efforts to monitor active galactic nuclei and provide near real-time alerts of transient events including stellar flares, asteroids and others of unknown origin.