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.
Olivia - Your new best friend built with an artificial neural network
Habitica - Habitica is a free habit building and productivity application.
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HabitBull - HabitBull
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Todoist - Todoist is a to-do list that helps you get organized, at work and in life.