The device is a vacuum that collects sufficient amounts of the dead person's remains (old dead skin, etc) into a single concentrated physical location to enable Miles to connect to them. (If there is a buried body, that is enough and the vacuum isn't required. But if the body is missing or cremated, the body matter must be aggregated using such a device.)
The device emits a hallucinogenic chemical into the air.
This device is a compact version of whatever powers the island. The spinning mechanism is the same type of thing as the frozen donkey wheel.
The device emits a high electromagnetic field which enables the ghost of the boy Miles is talking to to be heard more clearly.
The device is simply a vacuum cleaner or something similar, used to create noise so that Mrs. Gardner wouldn't hear what Miles was talking about with the deceased grandson.