Roof-mounted miniature helipad mailboxes, painted with QR codes. Really, why don't houses already have package receptacles for UPS and FedEx?
Although with these, I don't see why window box style package drops wouldn't appear. All it would have to be is a rigid mesh frame so it's not affected by wind/rain/snow, which would also make it light weight so it could be constructed easily large enough for the mini helicopters to make drops into. Put the QR codes on a sticker that goes on the window like an alarm company sticker.
I know the first response will be "that'll never happen", but it would allow package delivery any time, anywhere. Live on the 5th floor of a walk up? Your new game will be waiting right outside your window when you get home.
I honestly imagine there would be high demand for this for courier services.