The auto-jet was the Master's contribution to the Nestenes. Auto-jets took the form of plastic daffodils, each cell imprinted with instructions of a human nose and mouth. When in contact with signals from a radio, the auto-jet would seek out a human and spray a thin film of plastic at their face. Covering their nose and mouth, the target would die of asphyxiation and the carbon dioxide would dissolve the plastic, removing evidence of the Nestene's actions.
Disguised Autons handed out hundreds of auto-jets to the public with the aim to cause a mass death and panic. In the chaos, the Master would materialise the Nestenes on Earth fully. This plan was defeated when the Third Doctor convinced the Master the Nestenes would turn on him. (TV: Terror of the Autons)