It depends on your setup. If your Wi-Fi router is backed up, the app works as usual. If Wi-Fi drops, you'll get a notification with an estimated remaining backup time. When you're home, you can connect directly over Bluetooth for full functionality. There is no cellular radio in the product.
If you want your app to continue working undisrupted during an outage, we recommend plugging your router into Backup or the connected Power Strip to ensure continuous power.