Today I did not have my watch (Forerunner 255S) with me during my workout, but I did wear my HRM Pro Plus. Would it be possible to somehow get the activity into my watch or Garmin Connect account, with the HR that is stored into my HRM?
I don't think so. But if you start the activity on the watch, wearing you chest strap, you can do a workout away from the watch, and the chest strap will sync the rest of the activity when you get back to the watch.