A free program for Android, by Yoda Labs.
The simplest way to start focusing the mind, and build power and control in the lungs, is through counting the length of time spent on each breath. This simple exercise is easy to pick up, can be applied in a number of situations (either at work, commuting, at the park or in the home), and is one of the best exercises to help you get a good night's sleep.
The most important benefit of this simple exercise is that it will help you to focus and concentrate on your breath, which is something that is very important for your well-being and your productivity.