The third part of the tutorial series on Tessel iBeacon technology focuses on building the emitter or publisher beacon, which emits a signal to a detector using Tessel's hardware and software setup. This tutorial details the process of configuring the Tessel board with the necessary BLE module and PubNub for establishing two-way communication between the iBeacon and the detecting user. Key steps include setting up the Tessel with required node modules, connecting to WiFi, and using JavaScript's PubNub module to manage communication channels. The beacon emits an AltBeacon signal, and the tutorial provides insights into advertising data construction and implementing PubNub for message exchanges. The guide emphasizes ensuring efficient code execution to prevent Tessel timeouts and explains subscribing to PubNub channels to facilitate real-time interaction with nearby users. This approach enhances the functionality of Tessel beacons by enabling them to communicate with users in proximity, demonstrating the potential of smart beacon technology.