As for me, this is the example of pleasant UI/UX for other similar apps: it is intuitive, with no noise and it literally feels like the owners really care about you.
Highly recommend to use it from time to time, when you need some rest during the working day or if you feel anxious.
One of the most important things about CenterMe - it has real and working tools from real (!) experts. I feel calm just because of this fact :)
Could be great to be able to choose one specific practice depending on the goal, for example to calm your mind right before bed.