It's just literally audio feedback telling to you go faster or slower based on your heart rate. It's no more dangerous than voice navigation while driving.
Apple just took a huge swing at Peloton and at home fitness startups.
Why cycle in place at home with a Peloton instructor, when you can cycle outside with a Fitness+ instructor? Why limit yourself to your stationary Peloton bike at home, when you can use a stationary bike anywhere?
Apple can and probability will beat out Lulu Lemon's Mirror on price using motion capture on an AppleTV smartTV or Ipad.
Only startup that stands a chance is Tonal b/c of their hardware providing value.