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.
Cold Turkey - Cold Turkey is a free productivity program that you can use to temporarily block distractions so that you can get your work done!
Habitica - Habitica is a free habit building and productivity application.
Stay Focused - More suitable with Google Chrome, this service enables you ensure you do not waste precious time on updating Facebook status or chatting with people.
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
Freedom.to - Freedom is a productivity hack that lets you block apps, websites or the entire Internet on iPhones, iPads, Windows and Mac computers.
HabitBull - HabitBull