Let's face it: Locks and keys are old technology. Really, really old: the earliest known lock and key for a door were unearthed in the buried ruins of a palace near the ancient Assyrian city of Nineveh, and date to 4,000 B.C.
We'll skip over a little bit of the intervening history. These days, homeowners can lock and unlock their front doors with a fingertip — as long as they're packing their smartphone. CNET has the story here ("Kwikset Kevo: Unlock your front door in a tap"). The system works over Bluetooth, explains the story: "With the smart device within about 4 feet of the door, you simply lock or unlock it by tapping your finger (or elbow or nose) on the lock face. An LED ring lights up green when the door unlocks, yellow when it locks, and blue while it's processing. A red flash denies entry."