ECONOMICAL SMART SIREN: many features packed into one compact loud siren, just a little over 3 inches wide! MULTI-FUNCTION! Use as a panic alarm, as a home intrusion siren, have it activate if a door or lid is left open too long, and use it as an alarm for water leaks* and high or low temperature and humidity* or all of the above! *Additional YoLink devices required, not included. WHY PAY A MONTHLY FEE if you can secure it for free? See below for the many ways your siren can respond and for you to be notified of off-normal events, from a high-temp alarm, to motion detected in the back yard, or a garage door left open too long (other YoLink devices required, not included) DEVICE-TO-DEVICE PAIRING allows for two or more (up to 128!) devices to be paired together, in such a way they will perform their action even without WiFi, internet, and power! (Battery-powered or backed-up devices). Perfect for security and other critical functions: pair your water leak sensors to your Siren Alarm, and to your Smart Motorized Valve. EVEN BETTER with a SirenFob! Pair one or more siren products to your SirenFob, then pair one or more alarm products (such as door, motion, vibration sensors - ideal for vehicles, RVs, and other mobile applications or where internet is not available. *Additional YoLink devices required, not included. Search for B0BRCX6HVK START SMART! A YoLink hub is required for full functionality, including for the app to work, to check battery level, etc, but your hub is compatible with a growing family of smart products for home and business! Search for B0BJJZH511 for a starter kit with YoLink Hub or search B09FSS95G9 for a SpeakerHub (our audio, talking hub). BATTERIES ARE INCLUDED! LOOKING FOR SOMETHING FOR OUTSIDE? Search B092QR82P1, B09V2DXPPW, B0BWYLT3JB, B0BZHPQ1PK WANT TO USE YOUR OWN STROBE, BELL, BUZZER, ETC? Search for B0BWYLWWV6