Alarmed (iOS only, unfortunately). It allows you to set nagging reminders with notifications and has great features for snoozing a reminder or setting up routine reminders.

It’s great for ADHD. I basically use it for my schedule I’ll have it remind me the morning of something (or the day before depending on the event), when the reminder comes up, I’ll snooze it to to just before I have to leave.

I had been using apples “reminders”, which just seem to disappear into the ether if you happen to miss the notification.