I can recall very specific calendar events that I missed because the notification disappeared on my phone. This problem happened more often when I got an Android Wear smartwatch because I flicked through my notifications too quickly.
Now, thanks to XDA developer Bartito, you can get bugged to death until you acknowledge that yes, you do have a doctor’s appointment today.
The app is Calendar Events Notifier. It works by reading your notifications, which you will need to grant permission to the app in your notification settings, registering that it is a calendar event and, based on what you have selected in the Calendar Events Notifier app, will trigger a recurring notification that must be specifically dismissed.
As if that’s not good enough, this app is also compatible with Android Wear. So your recurring-notification should show up as a card on your watch.
The developer only mentions syncing with Google calendar, so if you use a different calendar, it’s unclear if the app will work with that.