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.
Habitica - Habitica is a free habit building and productivity application.
Everyday - Take a photo of yourself everyday.
HabitBull - HabitBull
ididit! - The procrastination friendly habit tracker. Take notes, manage tasks, track habits.
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
Patterns App - Transform your routine with easy-to-log habits, from exercise to meditation, and night-friendly reminders.