A friend of mine is a speech therapist in a high school. She serves students who haven't been served well in speech improvement in elementary school. She also works with English as a Second Language students.
She told me that she used some of the concepts about language that she learned from applied linguistic classes. She took her native English speakers back in their language and pronunciation development to the point where their pronunciation and language rhythm skills were acceptable and then worked forward. For her ESL students, she devised methods for teaching punctuation, rhythm and intonation to help them sound more like native speakers - that's what they wanted, to minimize their foreign accent.
She was very proud of the success that her students had in improving their speech.