The closest I can think of would be something like GoodTask but it doesn't have e2e encrypted sync or Linux/Android support. Source: 12 months ago

More Power Users: Ad-free episodes with regular bonus segmentsThe Field Guides and Labs Thanksgiving Sale - MacSparkyGive the Gift of Relay FMDaring Fireball: iPhone First ImpressionsNotes — inside Mail — on Mac OS X 10.5 Leopard – 512 PixelsNotes in OS X 10.8 Mountain Lion – 512 PixelsReminders in OS X 10.8 Mountain Lion – 512 PixelsiOS 9: The MacStories Review, Created on iPad - NotesiOS and iPadOS 13: The... Source: over 1 year ago

There are third party apps that can show Calendar and Reminders together. If you want one that is primarily a calendar but can also show your reminders, look at Fantastical or Calendars. If you want one that is primarily a reminders app but can also show calendar events, look at GoodTask. Source: over 1 year ago

If you're on iOS I would recommend GoodTask, it's based on Apple Reminders and very customizable. Source: about 2 years ago

Have a look at goodtask, it's uh, good? Decent widget, calendar view, can do recurring reminders, notes facility, completion history for reminders (Did I take my pills? Yes, I just forgot). Source: almost 3 years ago

Have you seen wip.chat... I'm not really suggesting it (since they charge you money) but same idea of posting goal points/checkboxes. Source: about 1 year ago

Another concept that's interesting/maybe motivating is wip.chat though I don't suggest it (not free). But it's neat (public todo's). Source: almost 2 years ago