The Mysterious Monitor is a monitor that is used to display the status of a person. It has two plugs: a basic three-prong plug and a mysterious stethoscope that is put on the heart of the person.
When both plugs are in their respective locations, the monitor can be turned on. In doing so, it becomes impossible to unplug the three-prong plug until the monitor is turned off. It is currently unknown how it does this.
More information can be found in this document.