The march of training games continues into uncharted territory. Now there's a game to improve your hearing and listening skills! DS Chounoryoku tests the frequency range of players' hearing, and asks them to identify tones and spoken words. We can't figure out everything that's going on, but it's all hearing-based, and the art is surprisingly poppy and attractive.
There are also musical selections for aural relaxation. All of this from Milestone, who usually develops shooters like Radio Allergy and Karous. Their Chounoryoku homepage has a weird promotional video that doesn't really show the game at all.