Audiofile Engineering's Quiztones - frequency identification/training app
Audiofile Engineering's "Quiztones is a frequency identification ear training app for amateur and professional audio engineers and musicians. Quiztones uses frequency-altered tones, noise and musical loops to train your ears and help develop more acute listening and frequency recognition skills."
Quiztones is compatible with iPad, iPhone and iPod touch with iOS 4 or later. Visit the website here. $2.99 at theapp store.