Emailing reminders to customers

[Matt]

My wife is starting a practice and we have her setup with Outlook with
Business Contact Manager. I started thinking today that it might be nice if
Outlook had the ability to send out an email to her client for an appointment
that she has setup in her Outlook calendar.

For instance, she sets up an appointment in her calendar for next Friday. On
Wednesday an email is automatically sent to the contact/email address that is
associated with the appointment.

Does anyone know of a way to accomplish this in Outlook or with a plug in?

Thanks for any help.