Cochlear implants have improved the lives of tens of thousands of the hearing impaired by providing sufficient auditory perception for speech, but these devices are far from satisfactory for music perception. Many cochlear implant recipients, especially pre-lingually deafened children, have difficulty recognizing and producing specific pitches. To improve musical auditory habilitation for children post cochlear implantation, we developed MOGAT: MObile Games with Auditory Training. The system includes three musical games built with off-the-shelf mobile devices to train their pitch perception and intonation skills respectively, and a cloud-based web service which allows music therapists to monitor and design individual training for children. The design of the games and web service was informed by a pilot survey (N=60 children). To ensure widespread use with low-cost mobile devices, we minimized the computation load while retaining highly accurate audio analysis. A 6-week user study (N=15 children) showed that the music habilitation with MOGAT was intuitive, enjoyable and motivating. It has improved most children's pitch discrimination and production, and several children's improvement was statistically significant (p<0.05).