My Internet of Things project utilized two Particle Argon boards to detect if there was motion in a room to control the status of a light. The two Argons were subscribed to each other so they could send and receive messages. The Argon with the motion sensor publishes a 1 when motion is detected and when no motion is detected it publishes a 0. If the second Argon reads a 1 the light turns on and if it reads a 0 the light turns off. If there is a change in the status of the light the second argon will relay this information to the first Argon which will flash its own led to confirm that the message was successfully transferred between the two. A website called ThingSpeak was used to record the data from the two Argons.
Project Details: https://www.hackster.io/group-20/megr-3171-iot-motion-sensor-c6e304