Imaging atmospheric Cherenkov telescopes (IACTs) are among the largest and fastest optical telescopes in the world, ideally suited to searching for nanosecond-timescale optical transients. These could be astrophysical in nature, or even associated with signals transmitted by extra-terrestrial civilizations. I will describe the methods used to extract such signals from data recorded by the VERITAS telescopes. A definitive test of these techniques is provided by measurement of a LIDAR on board the CALIPSO satellite, which also holds promise as a unique calibration device for IACTs. I will also discuss the potential of the converse approach – using telescopes designed for SETI to do gamma-ray astronomy.