Scheduled email reminders.

I was approached by an existing CMSB client about creating the ability to send scheduled email reminders to his many customers based on selections they make when signing up for reminders to do various routine self-service tasks. It would also be used to remind about upcoming routine scheduled maintenance service calls. They could respond by email or phone to verify or reschedule the service call.

I would use the membership add-on for the customer database management and add the required fields for reminder options, but am unclear as to how to monitor the data and fire off the emails as scheduled.

Has anyone done such and if so would I need any custom programming by the fabulous IT developers? If so would not be averse to paid help ... this is a rather important request for my client.