If i understood correctly, what you are trying to do, is to use your own computer as hosting for two instances of statping in subdomains.
I can assume you have all the network part solved, (ip address changes, ports open in your router, etc.) since you comment that you can access the page from outside your network adding the port in the URL.
Scenario 1- Statping uses is own http server, in this case you can change the ports xampp is using to clear them, so statping can use the standard ports, i have my local environment in port :8888, this is taking in consideration you are not using xampp to serve other websites that need standard ports. Im not familiar with statping or the web server it uses, but i highly doubt you can run 2 instances in the same port.
Scenario 2 - Serve the statping instances using xampp, to do this you can configure apache virtual hosts, you have one instance of the web server with will identify the header to know wich status page should serve.
this guide can help
https://www.cloudways.com/blog/configure-virtual-host-on-windows-10-for-wordpress/