In the mid to late 1800's, it seems we had a widespread fear of being buried alive -- a fear you can see played out in the quantity of U.S. patents issued to inventors hoping to innovate coffin technology. From the patent for a "Coffin To Be Used In Cases Of Doubtful Death," awarded to Christian H. Eisenbrandt in 1843, to the patent for "Improvement In Life-Detectors For Coffins" awarded to Theodore A. Schroeder and Hermann Wuest in 1871, nineteenth century inventors saw a market niche in catering to individuals who might wake from a coma and find themselves in a grave.
In a July 1999 feature on innovations designed to prevent individuals from being prematurely buried, American Artifacts writes:
At least some of these grave signals and life preserving devices were likely made and marketed, but I know of no examples or even advertising existing. It is not likely that grave signals would have been marketed to undertakers, since they would have been fairly confident that the corpse was not going to rise up after they had finished their work. However, some of these patents cover devices which can be pulled from the ground without disturbing the casket after an appropriate time had passed and the signal not activated. Making the grave signal recyclable for use on another grave would seem to have appealed to the mortician or cemetery operator, rather than the bereaved.
In the slideshow above, browse through some of the patents for technologies to prevent being buried alive, including Hubert Deveau's 1894 patent for the “Grave Signal," a coffin designed with a feature whose object "is to prevent the victim in the coffin from pulling down the rod and closing the air ports in case he should, in his paroxysms of agony incident to the discovery of his condition, grasp the valve rod."