There are a number apps available free from the App Store (Apple devices) and/or Google Play (Android devices). These include:
Kia Mataara - developed especially for Manukau Institute of Technology staff and students to learn some important aspects of Māori culture and language.
Te Reo Māori - Māori Dictionary by AUT
Te Pūmanawa - Māori Language and Culture App by Māori Multimedia (only the trial version is free)