I tried one of those "for ADHD" aps tiimo I think it was. It was great for about 3 days because it was new and exciting and the I just never used it again.
I use calendars for birthdays and for the people I need to gift I set up reminders to buy or send gifts that way. Anything I need to do goes in the calendar too or I'll forget about it.
Not so much an app but smart home stuff has been a game changer. I just setup my washer and dryer on a smart plug so I get notifications when my laundry is done. At some point I'll give myself reminders I haven't done anything with it too lmao. I also have lights turn on and off at certain times, doors auto lock after 2 minutes, I'm changing out my bathroom fans soon for humidity sensors, and I'm sure I'll come up with more.
Ohh app stuff. Scheduling text messages! Sometimes I forget people exist so when I remember I'll schedule a text or two for a few days later to keep a conversation going or start a new one so they're not always the one to text first.
I saw so many that I went and got checked and I was initiated into the club lmao