There aren't a lot of places creepier than graveyards. Why? There's something about a large collection of occupied coffins and tombs that makes everyone a little uneasy. Besides the idea of the dead (or undead) that gives graveyards a scary connotation, there's also a certain fear that keeps some people up at night: being buried alive. It's not fun to imagine, and (I assume) definitely not fun to experience. In the past (before certain developments in medical/post-mortem tech) the fear of being buried alive was not entirely unfounded. This fear drove people to innovate new ways to ensure that in case they were buried alive it wasn't a death sentence.
Most coffins are made a durable wood and sealed tight. Once six feet under, there's really no way to escape or let anyone know that you would prefer not to be in a coffin.
And if you were buried in one of these babies, you were definitely out of luck (iron coffins like this one were actually invented in order to transport the recently deceased across long distances.
One way (the most simple way, in my opinion) to prevent live burial was to have the body in question sit in a mortuary for a few days under close watch. Think of it as the "alive until proven dead" method.
Some thought burial vaults were a solution. If you was buried in a vault like the one below, just a turn of the wheel on the vault-door and you can scare the crap out of your grieving relatives.
"Ring once if you're alive." This intricate alarm system was integrated with the coffin so as to allow the mistakenly buried to sound the alarm and be sure their families keep them in a mortuary for a few days next time.
As great as these inventions are for alleviating the fears of those who think they may be buried alive someday, they only make things easier for the entities we all really fear deep down: zombies!
Back in the day, people spent a lot of time worrying about burying people and getting buried. It's good to see more people have hobbies now.