Google Tasks? Send the email reminder above, then open it in Gmail and click “Add to Tasks” in the toolbar.

Apple Reminders? There's no direct hook from the web — download the .ics to get it on your Calendar with an alert, or say “Hey Siri, remind me about this” while viewing the reminder email.

Microsoft To Do? Flag the reminder email in Outlook and it shows up in To Do's “Flagged email” list.