While Plivo’s systems do not perform health checks on your Inbound message URLs, they do monitor inbound message delivery rates. In cases where your message URL is unresponsive, we will start seeing a drop in inbound message delivery rate. 

You can enable SMS delivery alerts for your account which will enable you to receive emails whenever we observe a drop in your inbound delivery rates. 

For more information on how to enable delivery alerts for your account, check here