Already have this feature – HiFutureSelf - Future Messages Review

It does what it says. But honestly the reminder app that comes on every iPhone does the exact same thing as this app. You can set a reminder for any time in the future and it'll pop up on your screen reminding you to do that thing at that time. From what I can see this app does the same thing.
Review by sig33333 on HiFutureSelf - Future Messages.