Called the Ring-Con, it is a rubber fitness band that you can place a Joy-Con controller into in order to interact with dedicated game, Ring Fit Adventure.
You also get an official leg strap with the game, with both tracking player movement through numerous fitness activities.
The game takes players through an "expansive world", where they will encounter enemies to battle. They do this using real-world physical exercise - for example, jogging on the spot will move a character and squeezing the Ring-Con will attack.
There are challenges for different fitness levels and body types, and Ring Fit Adventure can be tailored to different players' level of skill.
"It’s in Nintendo’s DNA to keep thinking of new ways to entertain players and put smiles on their faces, and Ring Fit Adventure for Nintendo Switch is a new kind of game where fitness meets adventure," said Nintendo's European president, Stephan Bole.
"I hope that once players hold the Ring-Con, put on the Leg Strap and start playing for themselves, they’ll be immersed in a journey that will keep them motivated to come back and have fun exercising every day."
Fitness has been part of Nintendo's console plan in the past, with the Wii Fit board first being introduced in 2008. However, unlike the board, the Ring-Con seems to have a variety of different interactions and, by introducing it with more of a game than a fitness application, seems a great way for all the family to get involved.
It will launch on 16 October. The UK price is yet to be revealed although pre-orders will open soon, so we should know more then.