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.
Bucketlist.org - Log and catalog all the stuff you want to accomplish before you expire.
Habitica - Habitica is a free habit building and productivity application.
List Challenges - Earn points for your life experiences. Find lists that interest you, and mark off what you've done.
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
Life Listr - ***AS FEATURED BY APPLE***
HabitBull - HabitBull