…change your Raspberry Pi to security system. You get a notification when someone breaks into your property. Alternatively, you could monitor your children what time they arrive at home. Additionally, magnetic sensors are able to detect opening of the door.
Task example: If the PIR sensor or the magnetic sensor is triggered, Raspberry Pi checks the status of the mobile phone. If the mobile phone was disconected from Wifi, a notification mail will be sent, and the output “Siren” will have been turned on for 120 seconds.