THAT WAS EASY! Installs in moments: scan the sensor's QR code, give it a name, peel off the pre-applied 3M brand mounting tape protective plastic, press the sensor and magnet to the door and frame, and you have added security to your home or business! | WHY PAY A MONTHLY FEE, when you can secure it for free? Self-monitor and save when you take advantage of our many ways to be notified of alarms and off-normal events in and around your home or business. See "Know Now!" for more information! | MORE THAN JUST A DOOR ALARM! Place a sensor on each exterior door and window to 'Protect Your Perimeter' Activate and control lighting. Place a sensor on your fridge/freezer door or lid and know if it was left open, to prevent food loss. Track activity in your home or business. Keep an eye on children and elderly loved-ones. Use the sensors to protect liquor & medicine cabinets, gun safes, storage lockers & boxes. | DOOR AJAR! Our unique Door Left-Open reminder can be used to alert you to a door or window left open too long! You define the maximum time. Use our SpeakerHub, our audio hub, to play a tone or message, alerting you when a door is opened or left open too long. | NOT YOUR FATHER'S DOOR SENSOR! This is a sophisticated electronic device, utilizing the latest technology. 24/7 cloud server device supervision monitors your system for online presence, signal strength and battery level, to ensure it will work when you need it! (Hub required, for full functionality) | DEVICE-TO-DEVICE PAIRING: a unique feature, two or more devices can be paired together. Even if the internet is out and the power is down, they will carry out their paired actions. Pair your door sensors to a Siren Alarm, then turn it off when you want to "disarm" your system. Use a SirenFob or FlexFob to control your siren. Make your own custom security system! | DON'T TRY THIS WITH WiFi! LoRa is short for Long-Range. Boasting up to a quarter-mile open-air range, and operating at the 900 MHz band, YoLink devices can be placed where your WiFi probably can't go, such as in basements, separate buildings, even on RVs and boats stored on your property! Prepare to be pleasantly surprised! | SMART OR STANDALONE, you decide: for full-functionality and the full potential of your Door Sensor, a hub with an internet connection is required. Or, you can use device-to-device pairing to pair your door sensors directly to a siren - you can then manually arm/disarm your siren with a SirenFob (search B0BRCX6HVK). Search B09FSS95G9 for the SpeakerHub, or B07TQLKQLJ for the Original Hub. | BATTERIES ARE INCLUDED! Six AA batteries, preinstalled, good for 2+ years standby, are included! | Looking for a starter kit with hub? Search B0BZ88QB5P for SpeakerHub, or B088ZFGX3S for regular Hub. Looking for a Siren Alarm? Search B0887SMPKK. Looking for a garage door sensor? Search B07Z7QQV8K. Looking for a gate sensor or door/window/lid sensor for outdoor use? Search B08P1VQMCR