PetSafe Electronic Pet Door

Your dog gets a door key. The neighborhood possum does not. The PetSafe Electronic Pet Door responds to a waterproof key worn on your pet’s collar, allowing keyed pets to come and go without turning the flap into an open invitation. This large model accommodates dogs up to 100 pounds.

Homes where letting the dog out has become everyone’s unofficial second job are the fit here. You can program selective entry, exit and automatic locking, and the door supports up to five collar keys. That gives a multi-pet household room on the guest list, without requiring a human doorman for every backyard inspection.

It does ask for some commitment: installation in an interior or exterior door, plus four D-cell batteries that aren’t included. Wall installation requires a separately purchased kit. It makes the most sense if you want collar-key access control, rather than simply a flap that swings for whoever noses through.