This Set Of Three Wifi Door Sensor Detectors Is Compatible With Alexa And Google Product Features Receive Real-time Alarms Remotely:when door/window is opened or closed, the sensor will push instant notification to your smartphone immediately. so you don't have to worry about your baby going out of house without notice, will easily know when your aged parents leave or arrive home and even can be clear when someone enters your home,shop,office ,etc. Compatible with Google Play,Andriod and Ios System:No hub required and No fees charge. Convenient for you to detect the status of your doors, windows, cabinets, drawers or anywhere you want to notified when it is opened or closed.So you can travel or go to work or go to schoon or go shopping worry-free. Alert message push: Protect your home with open / closed door detection. When the door / window is triggered, you will receive an alarm signal from your phone. Home Security Alarm make House more safety. Easy Installation?No Need to use complicated tools when installation,just use 3M glue to install,firm and durable.The two arrows are opposite,the distance between the two compopents should be as close as possible,and the closest distance should not affect the opening/clsoing of the door or window. Low Power warning: The sensor door need with TWO AA Batteries(not include).When the battery level is low, it will automatically push messages throuch APP to remind you to change battery, never worry about running out of battery. Shipping: Shipping is complimentary within the lower 48 US States. We Do Not Ship to PO/APO Boxes, HI or Alaska We Do Not Ship Outside of the Continental US All items ship within 24-72 hours of Payment For large items that require Freight shipping a valid phone number is required to call and schedule your delivery Terms of Sale and Feedback: Feedback is extremely important to us and If you are satisfied with our transaction, please take a moment to leave Positive Feedback. YOUR Satisfaction is our #1 Priority! If there are any issues, PLEASE contact us BEFORE leaving a neutral or negative rating so that we may resolve any concerns. We PROMISE we can make you happy if you give us a fair chance. Returns / Concerns: All items qualify for returns within 14 - 30 days of receipt. Buyer is responsible for return shipping on any item that is not damaged Please be sure this is an item you want before making your purchase. Customer Satisfaction is our TOP priority! All items are IN STOCK at time of listing. Inventory changes constantly and it is impossible to maintain a perfectly accurate count of all items. Please do not penalize us if we have to issue you a refund! Thank You For Your Business!