Set-top boxes are in most every household nowadays, but they don't precisely turn TVs into Smart TVs, not in the same way that Raspberry Pi and Equiso can.
Western Digital figured it may as well add some extra functionality to STBs, and it chose gaming.
Though nothing heavyweight will work, the future WD TV Play will allow owners to use portals like Funspot and PlayJam to play Sudoku, Texas Hold 'Em and other casual games, provided people don't mind using the normal navigation buttons on the remote.
At any rate, the new WD TV Play will be available soon, with a remote featuring dedicated buttons for Netflix, Hulu Plus and VUDU.
As for performance, 1080p video playback, from all common formats, will run smoothly at 30 fps. Go here
for the FCC filing itself.