I bought this app, because it seemed kind of miraculous, then I tested it in an original song I recently recorded.
It works well when the recorded chords are simple triads and Dom 7th chords, but goes a little wonky if it encounters anything more complex. For example, when it encountered a D7#9 chord, it sometimes thought it was a D min 7 (understandable), but sometimes thought it was a CMajor, or an F#dim7. One quirk it has that is pretty consistent, it that it has a blind spot for IV (sub-dominant) chords: it consistently sees them as minor versions of the I (tonic), a weird idiosyncrasy.
Its a pretty useful tool, in some respects--sometimes you are stuck trying decipher a specific chord, but it will take a lot of interpretation to truly make use of it. If the music youre trying to figure out uses simple chords, its quite good.