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.
University of Reddit - Learn 1,000's of new things, from reddit
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
reddit shell - Web-based shell for browsing reddit (pretend you're working)
HabitBull - HabitBull
Reddit App - The official app for Android & iOS. Meow.