Making phone calls

Let’s discuss the situation in which phone calls make sense by considering the alternatives.

SMS delivers messages as text. These messages can be delivered to any type of phone, even what is called a feature phone. However, SMS utilizes a methodology called store-and-forward. SMS is not an emergency service; the network will use a best-effort approach to deliver the message, but delivery could be delayed for many days.

GPRS delivers messages over the internet. This is immediate, but the message will end up on the cloud, from where a notification would need to be sent to a smartphone, or the end user would need to have a dashboard open in order to see the notification. In such a case, any device that doesn’t have access to the internet, or that isn’t smart, will be unable to get this information.

With the preceding information, how then could we implement an alarm? How might we implement a smoke alarm that would be guaranteed to notify...