Easy as it can be: Take a picture and set a reminder.
At the date or time you choose your picture will pop up as a notification.
Very useful to remember to not forget to
- bring something with you
- fix something
- do something
- buy something
- birthday or christmas presents and even ideas for it
Subtile because you know what to do when you see the picture.
You can change the notification date anytime.
And you do not need to type.