I’m always tracking my exercises with my Apple Watch. So far I have been using the native fitness app and during (for instance) a spin class I keep my phone in front of my to more easily check that I’m in the right pulse interval (initiating a workout on my watch opens a widget on the iPhone Lock Screen) Twisting my arm to check my watch is much takes my out of my “mental zone” much more than constantly having it right in front of me on the handlebar. Since workouts from other apps aren’t imported for some reason, I suggest you create a similar widget so cardio exercises can be tracked on the phone.