Excellent
I found this app a couple of years ago looking for breathing exercises for asthma, as slow breathing techniques help to relax the airways. I quickly found, in addition to this, that the relaxation helped in a variety of stressful situations as well. I like that the sound settings can be customised, balancing the tunes with the nature sounds in a way that suits you. I don’t usually buy apps (I usually stick to the free versions), but I bought the full version because I honestly feel it was worth the money.