Some initial feedback:-
I’ll be using my ear(1)'s without my phone (when I go running I use a great little Spotify player called might vibe bemighty.com) and the tap and hold to change between noise cancellation/transparency/off would be better if it gave the letter in your ear for the mode you switch too e.g. N or T or O instead of different sounding beeps.
I’m trying to memorize which sound was associated with what cancellation mode, and still after many months of using them I’m still not getting the hang of it. I think this idea is great.
Similar discussions were thrown here, but more on the customization side. Maybe this feature you suggested could also be customized by the user, maybe allowing you to record whatever sound you wish shall be presented in your ear when changing modes! 
