Helllo is about doing, not reminding. With Helllo you write the message you want to send later (birthday greeting, anniversary wishes, personal note on a holiday) and Helllo makes sure the message is delivered on time.
Meet someone new - write them a personal message while the meeting is fresh. Finish a first date - write your note and make sure the date is for at LEAST 48 hours later. We're all busy, we lose track of time, we forget what day it is, and sometimes we need a way to write a message now, but send it later. Done. Meet Helllo.