Android Bombs are self-destruct devices created by Dr. Gero and used by the four androids that appear in the manga.
The bombs are implanted in the chest areas (apparently on the heart) and can be triggered either by the android themselves, or via a remote control. They were originally intended to keep control of the Androids, ensuring that they could easily be destroyed if they turned against their creator. The strength of the bombs seems more than that of a nuclear bomb, as Bulma is very amazed to see an abnormally large "Neutron readings" when she exclaims this to her father. It can be assumed that the bombs have the strength to destroy even Perfect Cell, as implied by Android 16's attempt at using them, though Cell himself seemed to scoff at the idea a mere bomb could destroy him after the failed attempt.
Android 18 threatened to activate her bomb against Cell when he tried to persuade her to be absorbed by him. She also used the same threat against Super 17 in Dragon Ball GT though this time she was buffing as she was aware it had been removed by Shenron due to Krillin's wish to remove her and her brother's bombs after the Cell Games.
Video Game Appearances
The bomb activates whenever Android 16's Ultimate Blast is used.
In Dragon Ball: Origins 2, their is a side mission where Android 8 visits Senbei Norimaki in Penguin Village to have his Android Bomb removed by him instead of Dr. Flappe like in the anime. Presumably the side mission is a potential explanation for its removal that never occurred in the manga as Dr. Flappe's entire appearance in the anime was filler material.