Incorporating, or more accurately trying to incorporate, physical activity into a tvOS app isn’t easy. Apple TV is no Kinect or Wii. At this time, about the best you can do with “native equipment” is wave a Siri remote around in the air or pop it into a pocket and use it as a kind of pedometer when walking on a treadmill or in place.
I spent a bit of time reviewing some of the “greatest hits” of physical TV gaming from walking companions to boxing/cheerleading games (would be much better with a secondary nunchuck) to yoga/balance and so forth. The best of these look at a lot more than a single arm-action point of control.
If you don’t mind going cross-system, of course, you can use motion features already on iOS and project them (directly over AirPlay or indirectly through Bonjour, etc) to a tvOS app but we’re already now talking bigger, bulkier, more planning, less impulse use, and less tvOS “app” design.
In theory you can use a wrist strap of some kind with the Siri remote and rely on arm motion to model physical activity. The chances of flinging the remote remain quite high unless the remote is physical tied down to a forearm, requiring a well-designed physical adaptor.
Conclusion? At this point, Apple is wasting a strong health branding component with its Apple TV product. Between the watch, iOS Motion, and Health Kit, Apple TV should be much more proactive than apps limited to logging meals (still easier to do on an iOS device) and offering coaching advice.
Opportunity wasted, premature entry onto the market, or simply wrong aim/branding?