From Doona, this car seat warning solution features: SensAlert is the only child car seat alert solution with three levels of alert to keep your child safe, so they're not left unattended in the car. SensAlert detects the presence of a child on board and triggers the alert system when the caregiver moves away from the car (the smartphone loses Bluetooth connection with the SensAlert device).SensAlert is powered by the Doona™ app, and uses a cloud-based system to call and send messages, so it does not depend on the phone's signal or status. Compatible with most car seats and boosters Share one device with up to 3 users simultaneously 3 alert levels: phone notification, phone call to smartphone, and emergency contacts Set up to 5 emergency contacts in the app Connect multiple SensAlert devices to your app Do Not Disturb Mode temporarily suspends alerts when using a car seat carrier or travel system. The Smartphone Left Behind Alert adds an extra layer of protection if your phone is left in the car while your child is on board Automatic connection to the smartphone's Bluetooth Low-frequency Bluetooth signal Notification indicating that the device's battery is low Washable textiles Product dimensions (WxLxH): 0.7 x 8.2 x 7.1 in / 1.8 x 21 x 18.1 cm Product weight: 0.24 lbs. / 0.109 Kg Recommended ages: 0+ Material: Polyester, Jersey Polyester Technology: Capacitive sensors Device Compatibility: iOS: 11 or newer Android: 5.0 or newer Power Supply: 2x CR 2032 replaceable Duration: 1 year, based on average use of 1 hour per day Operating temperature: -20°+60°C Imported.