The app will send push notifications when the first window is opened and the thermostat is turned off. Then when closing the window contact you'll get a push if any windows are left open.
The push notification will contain the names of the sensors still open. Once all contacts have been closed the furnace will turn back on and send a push notificaiton.
If someone turns the thermostat on before all contacts are closed, the thermostat will be turned back off and a push notification will be sent telling you which windows are still open.