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.
The Chum Detonator was first used by Plankton to blow apart a wall in the Bikini Bottom Jail. It was successful but the Prison Guards covered up the large hole with their bodies. However, they got stuck in place and Plankton and his cellmates went out through the front door.