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.
Jenkins - Jenkins is an open-source continuous integration server with 300+ plugins to support all kinds of software development
Habitica - Habitica is a free habit building and productivity application.
CircleCI - CircleCI gives web developers powerful Continuous Integration and Deployment with easy setup and maintenance.
HabitBull - HabitBull
Travis CI - Focus on writing code. Let Travis CI take care of running your tests and deploying your apps.
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.