Apple Fitness+ won't need an Apple Watch to work starting this fall
The Apple Fitness+ service will no longer be Apple Watch-centric. The company reaffirmed its plans to allow iPhone users in the 21 countries where Fitness+ is available to access it even if they don't own Apple's smartwatch. The iPhone-only users will get access to over 3,000 workouts and meditations. You can also still use the service on the iPad and Apple TV.
Understandably, the Apple Watch will get more accurate stats than just your phone. The iPhone will estimate the calories you burn, adding to the progress on the Move ring.