Hello @Anonymous ,
You can have a power app that has a start button. On select : create a new item in a SharePoint list.
The SharePoint list could have the following column:
Email - Who ever clicks the button in the App
Now create a flow in Power Automate, with a trigger of when an item is created in SharePoint.
In the flow, send an email to the user from the list item properties (Email)
Now add a delay action, add the you want to wait before the next email. And so on.
note that I say email. But this can be any form of alert from within the Power Platform connectors.
thanks!