Habit Tracker is now in Labs for everyone with tracking of daily activities, habit pausing/resuming, habits relevant only on certain days of the week and habits which you can practice multiple times within a single day. You can use it to track bad habits you want to get rid of too!
In the settings, you'll find a new section called Labs which is a place for trying out new experimental features. To enable Habit Tracker, visit Settings > Labs and turn it on.
Now you don't need an invite to start using the app, just download it and start using it