Microbomb

Microbombs are incredibly small explosives placed on a person's body and set to explode whenever that individual dies, meant only to destroy that specific person's body. They are used to make sure that a person's body nor important items can be retrieved by the enemy and were primarily utilized by the Cobra Unit in the 1940s - 1960s.

A possible device built upon the concept of the microbombs seems to be something that causes the FROGS of Metal Gear Solid 4: Guns of the Patriots to be cremated by blue fire upon their death, turning them into a black, ashen shell.