The thin mist saturating many habitats is acutally its primary police force. A type of utility fog, police fog is usually deployed to entirely permeate public spaces. Its use is often seen as heavy-handed and indicative of a police-state.
On its own, any given fog-bot has only basic functions, able to attach to its neighbors, relay information, sense its immediate surroundings, and emit tiny amounts of light. Working together, however, the fog becomes capable of many tasks. The fog can rapidly coalesce, impeding sight and even movement. Combing the poor senses of each bot produces thorough and fine-grained surveillance of the filled area. In addition to mesh-based communication, they will often relay messages through light or ultrasound, making them difficult to jam. Each unit can emit colored light, which, when coordinated, allows them to form signs and holograms.
Engineers are working to add even more functionality, including fire-fighting, and neutralization of hazardous materials.