mDecks has released version 4 of their Tonal Harmony study aid, Mapping Tonal Harmony Pro, along with a great demo video.
Mapping Tonal Harmony Pro has been envisioned as auxiliary material in the study of Tonal Harmony. The main objective of this app is to provide the student, teachers, composers and/or songwriters with a tool that will aid them in hearing, analyzing, foreseeing and composing harmonic progressions without struggle, in all keys alike.
The map has seven levels of complexity, from the basic diatonic neighborhood advanced secondary functions in major and minor modes and is viewable in all 12 keys and enharmonic spellings, plus a functional view (relative to the tonic). Each level is also accompanied by its respective workbook available at mDecks.com for further study and research.
All of that might sound boring, and the promise of Beethoven might not have you very excited either, but I think this video does an excellent job of demonstrating how you can explore harmonic relationships in the app. This is some high-level shit, and it is only $5!