[over9k] used his Arduino to set up a laser trip wire. The laser is mounted along side the Arduino, reflects off of a mirror, and shines on a photoresistor that interfaces via a voltage divider ...

Instructables member Patrick Panikulam has created a versatile wireless Arduino pen plotter and laser engraver, powered by an Arduino UNO microcontroller ...

You’ll learn how to build and program a motion detector with a laser tripwire, a long-distance Bluetooth listening device, a voice modulator, and even connect anonymously to the internet.

The Daytripper does that all for you, using a laser tripwire that automatically hides contraband apps or websites whenever it’s triggered.