The better the quality of your head phone is, the better your score will be.
There are thousands of chords, but all these chords are nothing more than a few chord types that are being transposed to different keys. If you learn to recognize the most important types, you will recognize the majority of the chords that is being used in classical and in popular music. Chord types like major, minor, dominant, diminished, augmented, minor major, dominant flat 5, half diminished, major flat 5, double diminished et cetera.
The paid version (Recognize Chord Types by Ear 2) has been built by a classical trained composer for advanced students of Harmony. This is the free version for amateur musicians.
As an extra you can download a free paper on chord types from http://composer.rowy.net/
This app is free and Ad-Free. Recognize Chord Types by Ear 1 has been designed for smartphone, but it will work on a tablet as well. Android 4.1.1 and up!