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.
Autohabit - Simple iOS app to develop good habits
Today - Visit the post for more.
Micro habits: Self-Improvement app - Super charge your self-improvement journey with Micro habits
Nirow - Habit tracking: Automated, Siri-ed, Calendar-ed, and More!