Hey, we’ve created an Arduino-based early warning system.

You’ll need two parts sets :

Transmitter:
-Assduino Uno
-nRF24L01
-Motion sensor

Receiver:
-Arduino Uno
-nRF24L01
-Buzzer

For the software side, you’ll need a library for the nRF module.

It will work the same regardless of the choosen module.
Antena just increese your range.

There are lots of simple types of sensors. You can send signals for motion, sound, or light changes.

During this project, I discovered something amazing about Doppler sensors. They can detect movement through wooden doors. I glued my transmitter to the door and created an extremely primitive but effective boss alert system!!
I went with the RCWL-0516, because it was the most compatible with Arduino.

You can replace the motion sensor with a vibration sensor. If you put the transmitter in your backpack or on your bike, you’ll know when someone is messing your stuff!