Most couriers know where their drivers are at all times. They should update their tracking shortly before delivery, so that people are ready to collect at the door. Email or SMS notification 30 minutes before delivery would be very useful. Some couriers currently phone before they get there to make sure that you are in before they even bother delivering, but that just doubles the chance for you to miss them because you have to be there for both the phone call and the delivery.
Websites that already offer SMS notifications and links to tracking websites could easily be notified by a courier’s tracking API and send out a SMS accordingly.
This would probably save a fortune in redelivery costs to couriers too.
Just a thought.