I have a 9VDC battery powered smoke alarm in my workshop and while you can hear it when it goes off in the workshop, you can’t hear it from upstairs or when nobody is at home. So I decided to retrofit an esp8266-01 to the smoke alarm to make it WiFi enabled so that it notifies me via SMS and email if the alarm goes off. I had to program in some logic rules to ensure the alarm was not a false one. As soon as the alarm sounds, the output of the alarm circuit goes high to about 9VDC which is then stepped down to 3.3VDC to power up the esp8266-01. The esp8266-01 is programmed with an inital 30 second delay before it attempts to connect to the local WiFi. Once connected to the WiFi, it sends the first of 3 SMS and email notifications to my mobile phone and email address via a 3rd party web based notification service. The second and third SMS and email notifications are delayed by 15 seconds each and provide verification that the smoke alarm has triggered and has been alarming for at total of at least 60 seconds. While the prototype has been working well, I have found that the esp8266-01 sometimes will not connect to the WiFi. This requires some further debugging and testing, however for less than $10 the concept works well.