If you never used TVii in its heyday, it was sort of like a universal remote-control with a native second screen experience. The Wii U Gamepad was used to browse a channel guide (generated by entering your zip code) and comment on TV shows. If you found a program you wanted to watch, the Gamepad's IR blaster would send a signal to your TV or set-top box to change the channel.
It was pretty novel way to tack TV-integration on to the Wii U without actually connecting the console to your set-top-box -- but it was also kind of slow, laggy and generally lacked support. Is anything of value going to be lost in its shut-down? Let us know what you think: the comments below await.