First off-- This is a PHONETICS app. Its intended for the study of sound production-- it would best benefit linguists and linguistic students of English, speech-language pathologists, speech therapists, and others who work with speech sounds.
This is by far the best app Ive been given for the study of speech production-- it is amazingly visual, clear, colorful, and has just the right amount of details. This app takes all the invisible movements of the tongue, lips, and teeth producing speech sounds and makes it visual. You can see every movement, placement, and variation. This app is one of the tools I use to teach.
I love this app enough to ask for a world-languages version.
Awesomeness 1D about Sounds of Speech