I guess it's really safe cause it's open source, you can make notes on your habits but don't really do that. Its simple. Really fast. Haven't found a way to connect it to notion. In general it's a great app to track you habits. Does its job. Not more, not less.
Youtine - Develop self-discipline, without using an app.
Habitica - Habitica is a free habit building and productivity application.
Wheel of Life - Self coaching tool for personal development and goal setting
HabitBull - HabitBull
Habit Challenge - Habit Challenge is an elegant mobile app that helps you to create new daily routines and keep you on track.
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.