Anectata, but I found that active wearables can help with initial motivation, but long term they become chore or even stressful when forced. I use them only for passive long trends tracking.

Our brains trick us to breath on defaults adjusted to our surroundings.

What I have found working to slow down breath is:

1st willful exercise repetition,

2nd changing surrounding environment and lifestyle (nature, decluttwring, idleness, peaceful eating, proper sleep)

3rd gaining awareness about trigger mechanisms (overcommitments, overexpectations)

It is all self-regulating. And pretty much what mindfulnes, meditation, prayer or forest walk brings.