its not so much a problem anymore. but there used to be quite of few people declared dead and buried alive. even now there is still a lot of people with the fear of being buried alive. look up some of the other devices invented so people could notify others if they were mistakenly buried.
If the mistress already has the billions you left her, fat chance she will come dig you up and risk invalidating your death and the will that left her the billions. "I'm sorry, you can't be my lover. He's dead." Click.
i bet the Arabs down in UAE have bought couple already since they spend millions on car number plate to properly show how rich they are... since a 1.8 million dollar Bugatti does not do the justice