Nintendo has announced Ring Fit Adventure, which is what they had previously teased this last week as can be seen in this thread.
You can view more details at the official site here.
The game will be out October 18th, 2019 for $79.99 USD.
Some impressions from The Verge below -
So how exactly does a fitness adventure RPG work? First, you wrap the leg strap around your left leg, and then hold the ring in front of you sort of like a steering wheel. Each level is on rails, with a few branching paths to explore. To move forward, you jog on the spot, and you turn by pointing the ring in whatever direction you want. To move faster, you simply jog faster. If you reach an obstacle to jump over, you point the ring down, squeeze it to gain power, and then release in time to jump. As you run, you can shoot bursts of air to smash crates, which again is done by quickly squeezing the ring and pointing at your target. You can also vacuum up coins hidden in each level by stretching out the ring to suck them in.
It can get intense even though the levels last just a few minutes; I found myself sweating after just two of them. You never really stop moving, and doing the various ring-related activities while simultaneously jogging is a decent workout. Things get even more challenging when you factor in the battles. They work sort of like a classic Japanese role-playing game. You’ll see an enemy in the level, and as soon as you touch it you’ll be thrust into turn-based combat.
To attack, you can choose from a variety of exercises. To do one attack, I had to hold squats for a few seconds, following on-screen instructions, while another involved doing yoga-style poses on the ground. After a few reps, you then switch to defense: in order to fend off attacks, you stand, press the ring against your abdomen, and hold, forming a shield to absorb your enemy’s barrage. This repeats until either you or the bad guys are defeated.