IoT Network Alarm is a device which checks that a defined remote host is online and sounds an alarm when it is unreachable.
Code is compiled for ESP8266 WiFi module which performs network monitoring and sounds an alarm.
The source code is available publically via GitHub with release notes and downloads available here.
To raise bugs or issues with the library, feel free to raise an issue on Github or feel free to contact me.
I also wrote a blog post chronicling the development of the alarm, which you can read here.