Hi @vadenhal 
Sounds like a cool idea for an app. In order of difficulty/complexity:
I’d recommend the date input component for this.
It might be possible to do this with the API component, but an no-code integration like Zapier or Integromat might the best bet? See more here:
The current Push Notification component isn’t really set up for this. I’d recommend that if you’re going with Google Calendar, for example, that when you create an event you also add in a 10 minute or 1 minute reminder before the event starts. That will ping your users when the need it.