The celebrated American inventor Thomas Edison, whose parents were Spiritualists, worked on an electronic device that sought to facilitate contact between the living and the dead. In a 1920 issue of Scientific American he declared:
"...if personality exists after what we call death, it is reasonable to conclude that those who leave this Earth would like to communicate with those they have left here... I am inclined to believe that our personality hereafter will be able to affect matter. If this reasoning be correct, then, if we can evolve an instrument so delicate as to be affected or moved or manipulated... by our personality as it survives in the next life, such an instrument, when made available, ought to record something."
Alas, Edison had not completed the machine by the time of his death in 1931, and he didn't leave behind his project notes (or a number to reach him at!).
--L.L.
Sources:
Fortean Times, "Distant Voices"
The Encyclopedia of Ghosts and Spirits by Rosemary Ellen Guiley