Smart Wifi Door Sensor: No Hub Needed, Wireless Window Sensor With App WiFi DOOR SENSOR WITH APP ALERTS: No hub required and No fees charge. Control with the "Tuya Smart" or "Smart Life" app. Get instant app free notification alerts on your smartphone when doors or windows open or close. Note: door sensor only works with 2.4GHz WiFi, not works with 5G. SPPPORTS VOICE CONTROL: Door alarms for home compatible with Amazon Alexa and Google Assistant. Alexa/Google is able to answer the question, "Alexa/Google, is the 'Device Name' Closed/Opened?" LINK WITH OTHER TUYA SMART DEVICES: The smart window sensor can control other Tuya smart connected devices as the status of the door or window changes. For example, Automatically turn on your smart wall switches or smart lights when door opened. LOW POWER WARNIGN BATTERIES INCLUDED: Door open alert powered by 2*AAA batteries(INCLUDED). Enjoy over six months of battery life with this door alarm sensor. When the battery is running low, it will automatically push messages through App to remind you to change battery, never worry about running out of battery. EASY INSTALLATION AND WIDELY USE: Install the smart door sensor with the included 3M sticker for a firm and durable hold. Install the sensor on gates, mailboxes, refrigerators, drawers, bedrooms, garages, yards, pet doors, and more. Gaoducash provides a 24-month warranty for the door detector, please feel free to contact if you have any questions.