Deep [official site] is a relaxation experience designed for Oculus Rift. I found it in the Leftfield Collection during Rezzed and I'm glad I did so early in the day. Later on it looked like relaxation in front of an audience as people nudged past or peered over.
In order to use Deep, you put on the headset and headphones while wearing a band just below your chest. You'll see an abstracted underwater environment with shoals of fish and plants and rocky chasms to explore. The band you're wearing is designed to measure how deeply you're breathing and it translates that information to affect your in-game buoyancy. Breathing in deeply causes the band to expand and your buoyancy increases. Breathing out makes you sink towards the ocean floor.
When I started playing the control system was lovely, letting you bob gently through the space, controlling the overall direction with your gaze. It's a self-made contraption, though - a first sewing and soldering project for developer Owen Harris - and at some point it slipped a little meaning I'd started to strain to get the band to note an in-breath.
Harris explains that the game is based around deep breathing techniques he'd learned to help deal with his own anxiety. He stresses that he's not putting himself forward as an expert teaching those techniques but that Deep simply uses the principles alongside an authored environment to create a kind of digital Zen garden which promotes relaxation in its players.
At the moment Deep is only available at festivals and events. There's a chance it might be getting a release later this year but Harris admits "I could happily work on it forever". Harris is also toying with the idea of multiplayer, where the rhythm of your breathing would help you seek out another person in the game.