Isn't annoying when you miss a parcel because you couldn't be home when the courier arrived? How's about making a secure box that can sit outside and allow a courier to put your parcel inside when you aren't home. Obviously to be lockable. So my suggestions are:
1) A keypad with a password or code that the courier must enter to open the box (increasingly online retailers allow you to add delivery instructions when you place an order)
2) Connect your doorbell to a device that will contact you when somebody is at the door (SMS, email or phone call maybe), perhaps the visitor could be viewed on a camera somehow. You can then remotely open the box (or tell the courier the code)