Hey  @Nelman,

You should be able to configure a connection alert for the smart plugs from within the Deco App:
How to Configure the Connection Alerts Feature on Deco

This will be the most reliable way of configuring this, as any methods on the Smart Home side would require the cloud to report that the connection has been lost, rather than your router being able to monitor/handle the request at all times. You may want to configure an IP reservation or name the device so that it can reliably connect and be monitored by your network.

If you want to look towards a smart home solution, you may be able to configure something like this through a third-party integration such as SmartThings or Alexa, but I am not sure.