I imagine this is just a website with the domain eth.xyz and with some subdomain shenanigans. You make it sound like it's sponsored by the TLD or something.
While $19 yearly is admittedly very cheap, 20 daily outbound emails seems like an absurdly low limit. I can't imagine many sole proprietorships (as they suggest as customers for that tier) would be able to sustain that.
This is a good idea and seems well-executed. While still essentially a gimmick, the portability is a much better and more useful gimmick than the Wii's motion controls or the Wii U's touchscreen controller. It seems to get in the way of gaming much less than those did.
Unfortunately, while it's a rather good gimmick, it seems like Nintendo is repeating its usual mistake of sacrificing gaming power for it. Releasing a device with a 720p screen in 2016 is almost as bad as releasing a device with a 400x240 screen in 2011, in my opinion.
Nintendo has a very bad habit of making devices that compete with the previous generation of its competitors' devices instead of the next one.