Agree! I could do this with my eyes closed if not for that. A simple "bip" noise or something.
There is an option under cue sounds, if you're using a phone I think you might need to take it off silent :) Let me know if that works.
No, I think you're possibly misunderstanding the issue. That option you mention allows one to change the sound used, which I suspect we all get, but instead the problem is there's no sound between breathing in and breathing out. You need three audible cues not two.