I think I'd want electrical isolation. WiFi gives really good isolation. Wired Ethernet can be pretty good ("Most Ethernet transformers are specified for 1500V

I think I'd want electrical isolation. WiFi gives really good isolation. Wired Ethernet can be pretty good ("Most Ethernet transformers are specified for 1500Volts RMS isolation") and I'd presume optical cabling is better. It doesn't take much fiddling with electronics before you make a good mistake you learn from! I do like their solution and it is obviously great for standalone GPIO that doesn't need any wired connections to the rest of the world.