I made a low budget laser tripwire. I didn't have a buzzer, so a LED turns on when something blocks the laser : r/arduino
How to make a Laser Tripwire Alarm using Arduino. – MYTECTUTOR
10pcs 3v-5v 650nm Adjustable Mini Laser Sensor Module 5mw Arduino Red Laser Spot Diode Copper Head Level Meter Ground Wire Meter - Sensors - AliExpress