I like to use this app to work on the receptive identification of sounds. Then, to keep the student engaged, after about 10 attempts, I usually "step it up a notch" by asking the student to say what they hear before touching the answer.
I encourage the student to use his/ her communication system to say "I hear" or "hear" and then point to the correct choice on the app. If the communication system has additional nouns or if the student is verbal, I may ask the student to use a complete sentence (e.g., "I hear a ______.") to work on commenting.
With some practice, I have seen some students generalize this commenting skill to comment on what they hear in their own environment ... " I hear a jet!"
It is worth the megabite usage on the iPad to give it a whirl!