When does the app use mobile data (I have a Samsung S8) and how much does it use? I have no cameras, just door and motion detectors. I want history, mode and notifications when I’m away, plus the ability to change modes, but don’t want to use any more cell data than is necessary. Do I have to be signed in to my account in order to receive notifications? What happens to data usage and notifications when I close the app on my phone?
It depends on your setup. Since you don’t have cameras in your setup then it should be rather minimal.
Depending on your phone you may (or may not) be able to turn off the notifications. On my phone I still get notifications even when the app is turned off.
Your phone is going to use Cell data as it does require some to communicate from your devices to your app to give you updates on status and those notifications.
About all you can do is to see, in your setup, how much data gets used. If you find out you need more and want to continue your setup then you’ll have to up your cell plan.