When I need to have my car repaired, I usually drive to an auto-repair shop, leave my car and ask the staffs if they can deliver my car to my parking space after fixation. In many cases, the detail shop agrees to my request and a delivery staff drives my car and park it in my parking lot on the ending day of fixation. On handing over of car key, I usually ask the staff in charge of delivery to throw it into my mailbox on the front door. But such an exchange may be possible under the condition that the distance between the parking space and my front door is not so far. If my parking space were distant from my front door, I would feel sorry for the detail shop's staff for spending important time on moving from parking space to the door.
In general, parking lots tend to be located remote from the car owner's residence especially in urban area, I guess. Considering such situation, I think the combination-locked storage pocket embedded under car surface is required. The store staff can leave the keys, envelope containing receipt or small change, if the car owner give him a unique key number in advance by phone.
As for me, I will use it for keeping a spare key when I have to carry too much luggage and have no confidence in not missing my key while walking around after getting out of my car.
