No, Nintendo of America hasn’t announced Wii Relax yet, but they are laying tracks for it. Nintendo registered not one, but three trademarks for Wii Relax in the USA. The filings cover everything from video games to trading card games.
Wii Relax is most likely a video game, though. One interesting thing to note is the spacing in the US trademark. It’s Wii Relax and not WiiRelax as seen in Europe. Vitality sensor launch game or not, Wii Relax appears to be a key product for Nintendo whenever it comes out.