Why don't you just set a reservation for such devices so when they boot, they always get the same IP.. Then you don't need a webpage to look you will KNOW what IP said device is.. OR just access them by name if you have pfsense set to register dhcp leases.
Best of both worlds - set reservation so pi1 is always 192.168.1.100 for example.. And then access it via pi1.yourlocaldomain.tld