The first is, my mailbox is across the street, and I'd like to know when the mail comes. So I have a Z-wave door sensor in the mailbox to send me a notification to my phone when the mailbox is opened.
The other is to nag us to move laundry to the dryer. I have a Z-wave power meter that my washing machine plugs in to, and another Z-wave door sensor on the door. When the power meter detects the washing machine stop using power, it waits a few minutes and sends a notification to unload every few minutes, until the door is opened.