PIR sensors (PIRs) use heat radiation from bodies to identify the presence of people and animals. This can be used for unlocking doors or starting a video recording.

Researchers designed an IoT network using sound and motion sensors that estimates public space utilization. The ideas can be applied to other IoT sensor networks.

In this security system is based on the embedded system along with GSM and sensor networks. The human movement is detected using the PIR sensors.

With just a Wemos D1 Mini, a standard PIR sensor, and some open source code, you can create a practical self-contained motion sensor module that can be placed anywhere you want to keep an eye on.