I have used the NanoGong voice recorder with a level four class. All students were given a text to read and practice. I chose so that the text had a majority of known words. Students were given time to practice reading it. By the deadline, they had to submit it to me for evaluation.
Each student had a different text. As a teacher, I wanted to see if I could understand the various accents. If each student does the same text, my brain has it after the second time and I'm not really processing the speech.
I gave each student feedback on difficult consonants particular and specific words they needed to practice.