FollowUpThen - The simplest way to schedule an email reminder
Memo to Me - Online email & SMS reminder service.
Followup.cc - FollowUp for email is a lightweight productivity suite that keeps your conversations and tasks from slipping through the cracks. Set perfectly timed reminders that arrive at the top of your inbox, right when you need them.
Date Reminder - Date Reminder reminds you of recurring or nonrecurring events, like birthdays, bills to pay...
Gmelius - Gmelius is the first collaboration platform designed for G Suite and your company's daily tools.
Free Alarm Clock - Free Alarm Clock is a free, full-featured and user-friendly computer alarm clock for Windows.