I'm sure it will improve-update, it hasn't.
First, for those that don't know(as I didn't), pressing the " home" key allows you to access your apps while maintaining your phone call.
I found the sounds to be great when not on a call but once connected to a live person, the sounds were barely discernable.
I'm sure this will improve with updates. The concept is very good!
UPDATE: Update finally came out for this app and I was really hopeful because of it's potential. The update made it worse for me. Those i call still can't hear the sounds and now it won't play sounds when phone is placed to ear (when screen goes black).
Again, great concept, horrible implementation = do not buy!