This is SNESoIP, an open-source project put together by a pair of Germans that lets you play original SNES games, using original SNES hardware, over the internet.
You could technically do this back in the day using stuff like XBAND, but it was terrible. This, despite it's been in development for only a few weeks, looks a lot easier.
The tech is pretty simple (and ingenious). Because the games obviously don't have any in-built online multiplayer options, SNESoIP simply plugs into a console's controller port and beams the inputs to the other console.
It's open source, so if you're crafty you can download information on how to build it yourself (and also donate to the creators as a "thanks!") here.
SNESoIP: The SNES ethernet adaptor [GitHub, via Motherboard]