Title mostly speaks for itself here. It would be great to be able to schedule automatic email reminders when creating invoices and payment has not been received. For example, 7 days before due date on a Net 30 or 7 days after a Due on Receipt if the invoice has not been marked as paid. Just have it send a fresh copy of the invoice & stripe link to the saved email address for the client with a "Reminder, payment is due in xx days" at the top.
The ability to email the invoice directly from the app is awesome, but I'm guessing many of us have a few of "those" clients and would appreciate the time saved constantly re-sending the invoice to someone who routinely forgets to pay them.