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.
Outlook Google Calendar Sync - Offers calendar synchronisation between Outlook and Google, including attendees and reminders.
Habitica - Habitica is a free habit building and productivity application.
GO Contact Sync Mod - GO Contact Sync Mod is an open source tool to synchronize your Microsoft Outlook contacts with...
HabitBull - HabitBull
gSyncit - gSyncit Outlook Cloud Synchronizer. Outlook Calendar, Contact, Task, Note Synchronizer supporting Google, Toodledo, Evernote, Informant, iCloud, AOL, Yahoo, Synology, Fruux, Memotoo and CalDav/CardDav services.
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.