Open Platform Management Architecture
Open Platform Management Architecture (OPMA) is an open, royalty free standard for connecting a modular, platform hardware management subsystem (an "mCard") to a computer motherboard. Platform hardware management generally refers to the remote monitoring of platform hardware variables such as fan speed, voltages, CPU and enclosure temperatures along with a wide range of other sensors.
Source: Wikipedia — Open Platform Management Architecture (CC BY-SA 4.0)