I thought it was nonsense when I first heard it, but the traditional paper system is actually more secure than a completely digital system. Here is a really good video explaining it: https://youtu.be/w3_0x6oaDmI
My wife wanted an app to list birthdays and anniversaries.
I wanted an app that would keep track of the gift ideas I had for people and to get reminders of these ideas as the birthday rolled-up. And that's how Planniversary was born!