The present disclosure relates to monitoring the condition of fluid extraction components associated with a subsea hydrocarbon drilling and production operation and, in an embodiment described herein, more particularly provides a sensor assembly for monitoring the extraction component which is easily installable and locally powered. The sensor assembly, in one embodiment, is contained on a patch. The assembly comprises a sensor, a power supply, and a communication device, all located on the patch. The patch can be easily coupled to fluid extraction components, such as a valve associated with a blowout preventer stack. The patch can include a coupling material on one side of the patch allowing the patch to adhere to the fluid extraction components. The patch can further include a power generator, such as a piezoelectric generator, thereby allowing for the sensor assembly to be locally powered.