Habitica - Habitica is a free habit building and productivity application.
Habit List - Create good habits and break bad ones with the app that keeps you focused.
When Did I…? - When Did I…?
Micro habits: Self-Improvement app - Super charge your self-improvement journey with Micro habits
HabitCoach - Habits to follow from the best life-changing books.
Autohabit - Simple iOS app to develop good habits