Now you can build a security system in no time, but the security is not limited to PIR sensors, you can add other sensors to it, such as CO₂ or gas, or sensors for detecting water leaks or smoke, and you can create a dependency between them. For example, if you have a broken pipe in the house and the water leak sensor detects water you will be notified in the Blynk application, but also another ESP8266 that is subscribing to the leak topic can close the main valve so the damage is limited by the time you arrive home.