A thought chip is a device used to connect to the thought network.
Dr. Bruce Tinner came up with the first concept of the thought chip, though his were designed to affect the visual part of the brain, rather than the audial, and connect with his virtual reality machine. When Eddie McKay and an AI destroyed the machine, a team of Dragonstorm scientists including Rudyard Shelton adapted them to their current function. (Disruptive Selection)
Most thought chips allow the user to send messages either to specific individuals or to everyone in range. Rudyard Shelton's is also capable of picking up messages not sent to him. (Survival of the Fittest)