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.
X (Twitter) - Connect with your friends and other fascinating people. Get in-the-moment updates on the things that interest you. And watch events unfold, in real time, from every angle.
HabitBull - HabitBull
Taskful - Deadlines, meet your match.
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
PopDo - A quick task list for your Mac menu bar