Quiztones is a nifty little ear training app from Pro Audio Files that lets you do your audio training exercises while in the studio or on the move. it can be a really useful tool in music production and developing your ear for music and mixing. places like Point Blank and SAE use ear training with their students, and out of the few i have experienced over the years this is by far the most flexible option out there at the moment. although it does have a few niggles id like to see addressed.
More info here - https://theproaudiofiles.com/quiztones/