Auto Resolve from System Checks

I have a client to whom has a few buildings to which they provide share office space for.effectively a coworking environment. Their sites do not have a dedicated computer on site where I can install a monitoring agent. Therefore, I dont really have a tool to do SNMP internally to the network gear. SNMP from the WAN is not something I am going to do because of security, so the only option I really have is to do is a ping system check from a computer over the internet to their external WAN IP to just let me know their firewall is on the internet. I do get an alert when it goes down, even some false positives as since I am going over the internet and cant change the latency, I think a few of the pings are beyond the latency pre-programmed in. In any case, there is no way that I have found to have it auto clear the alert if the ping comes back. I cant use Automated Remediation because the alert never changes when it goes back online. Can it be programmed so that when a system check can ping again, that it clears the alert?