Miniature Audio Transmitters are often used by John Casey and Sarah Walker to listen in to what is happening to Chuck. They can be concealed in many things. Some notable ones include: * A picture frame (from "Chuck Versus the Sandworm") * The RK7 mini mic; a tie pin shaped like a guitar (from "Chuck Versus the Imported Hard Salami") * A watch (from "Chuck Versus the Imported Hard Salami")