The TriFlo is a very good incentive spirometer.
Ultrabreathe is a small device that helps you to control your breathing.
The following video explains you how use the flow ball. It is a breathing device that allows us to work the air stream in an enjoyable and fun way.
The Breath Builder is a very usefull breathing device to improve your sound.
Here you have a infographic that show us three breathing devices to improve our sound.