STT Himi is an educational application under the category of Books, designed to provide access to STT Himi and Hiva Usu for users on their iPhones. The hymn content is affiliated with the Free Church of Tonga (Siasi 'O Tonga Tau'ataina). The app is currently in development, with upcoming features and updates promised in the future.

The STT Hymn App offers users the ability to search for hymns by numbers and titles, save favorite hymns to a personal collection, share hymns online, access Papi and Mali lyric content, switch between Day and Night Mode, and explore Hiva Usu songs, with ongoing updates. The app also operates entirely offline.