Just wondering if you're considering adding Meditation in the activity?
Breathwork is good but the meditation I do is more than 5 mins and I don't want vibration during the meditation.
It shouldn't be too hard as it could be very similar to Breathwork (monitoring heart rate, stress, respiration rate etc) without vibration and be able to end by tapping on the watch.
I believe this activity would be very useful as Meditation is quite popular.