@OP
If, for some reason, you can't schedule an email then you may try scheduling a SMS via some web service. You can send a link to uploaded stuff (notes, video/audio message etc) via that sms.
The reason I'm not recommending scheduling WhatsApp is because that option is, as far as I know, dependent on your mobile still being on, having internet access and praying that your mobile operating system doesn't kill the background process of that 3rd party app.
Whereas scheduling an email or a sms via a web service doesn't require anything other than typing your message and clicking on scheduling.