The Chum Detonator appears to be a combination of Plankton's chum and a simple bar of soap. It also has wires going through it.
Role in episode
The Chum Detonator is first used by Plankton to blow apart a wall in the Bikini Bottom Jail. It is successful but the Prison Guards cover up the large hole with their bodies. However, they get stuck in place and Plankton and his cellmates go out through the front door.