Free printable trackers
Paper still works, and it works better when the dates are already right. Customise a sheet here, print it, and stick it somewhere you will see it. Nothing you type is sent anywhere.

When the paper stops working
A sheet on the fridge cannot remind you at 8pm, and it does not come with you. HabitKeep is free to download, with reminders, Home Screen widgets, an Apple Watch app and sync across your devices.