Interesting concept; 3rded that I couldn't figure out the first scene without instructions. Clever mechanic for sort of synchronizing breathing. One interesting thought I had in the same direction (VR meditation trainer) is that tracking is sensitive enough you can pick up breathing and even heartbeats just from the head and controller pose data; so in theory you could have the user put a controller on their chest/diaphragm, and do the right signal processing magic to get the data out.