Low-frequency acoustic waves (called infrasound) are used for monitoring atmospheric disturbances including nuclear tests, volcanoes, and other powerful phenomena. Brief but focused infrasound campaigns enable the study of a wide range of sites and phenomena at low cost and with few workers. However, the cost, weight, and general inconvenience of commercial data loggers has limited past infrasound campaigns. To solve this problem, I developed an Arduino-based infrasound logger (the Gem) with a fraction of the cost, weight, and installation time. The Gem has since been adopted by several institutions for infrasound recording at volcanoes, stratospheric balloons, and river rapids.