I have seen that whenever someone creates an appointment in A+, and the plugin is configured as AUTOCONFIRM=FALSE a message of pending appointment is sent to the administrator.
But I am the admin and am not in charge of looking at this site on a 'manager' type basis and I do not wish to make the Service Providers administrators.
I would think that the best would be to have a check box in the Notification area that enables "Send New Appointment Notification to Provider". You could have a secondary checkbox that stated "Send Copy to Administrator".
This would ensure that Service Providers get notification of their own appointments that are in the Pending state and need confirming.