Price a Chilean cemetary charges for an alarm built into coffins to ensure against mistaken live burial: $462
Here is some evidence on the likelihood of being buried alive.
The Italians take things further, albeit at a higher price:
In 1995 a $5,000 Italian casket equipped with call-for-help ability and survival kit went on sale. Akin to bleeping devices which alert relatives to an elderly family member’s being in trouble, this casket is equipped with a beeper which will sound a similar emergency signal. The coffins are also fitted with a two-way microphone/speaker to enable communication between the occupant and someone outside, and a kit which includes a torch, a small oxygen tank, a sensor to detect a person’s heartbeat, and even a heart stimulator.
What I would want: Satellite radio, Spenser’s The Faerie Queene, and a cell phone with a good battery.