Let me start by saying, this little red gadget has been a game-changer for my solo travels. The 80dB alarm is LOUD – like, 'wake up the entire hotel floor' loud. I tested it in my apartment first, and let's just say my neighbors weren't thrilled (but I felt super secure).

The installation truly is tool-free and takes seconds. I've used it on everything from flimsy motel doors to heavy Airbnb entries. The adjustable jammer worked on about 80% of doors I encountered – though thicker doors can be tricky as some reviews mentioned.

Battery life has been impressive. After 2 months of frequent use during business trips, mine's still going strong. The vibration sensor is sensitive enough to detect door jiggles but won't go off from normal hallway noise.

Now the downsides: It does add about half an inch to your door clearance, so very low-clearance doors might not work. Also, while the alloy construction feels sturdy, I did have one false alarm when someone slammed a nearby door hard enough to vibrate mine.

For $20? Absolute steal if you travel often or want extra home security. Just maybe warn your housemates before testing it!