Gabriel Bestard-Ribas got tired of his house keys scratching the smartphone in his pocket, so he combined them.
The result was a Goji lock, which senses when your smartphone is near and not only unlocks a door but greets you by name.
It's just one of the "smart locks" on display in Las Vegas.
"My keys were always scratching my phone, so I thought why not build them in," said Bestard-Ribas, founder and chief executive of San Francisco start-up Goji.
His creation fuses mobile internet technology with centuries-old lock mechanics. A free Goji application installed in smartphones uses Bluetooth connectivity to let the lock know a person is near and, if it is a resident or someone given a "digital key", a personalised welcome message is displayed and the path is opened.
A camera built into the lock takes a picture of whoever is arriving. Images of visitors as well as alerts regarding entry are relayed to residents' smartphones through home wireless internet connections.
"It is about allowing you to feel confidence and control over your home access," Bestard-Ribas said. "We have all lost keys or given them to someone who left our sight; we don't know if copies were made."
Temporary digital keys, restricting use to specified time periods, can be e-mailed to house cleaners, dog walkers or others who may need to visit homes. The locks cost US$299 and will be available online from March.
Veteran lock makers Kwikset was also showing off smart locks. A Kwikset Kevo lock senses when a resident's smartphone is near and then opens when the person touches what appears to be an ordinary deadbolt in a door. Kevo launched late last year with an application tailored for iPhones.
Schlage's touch-screen deadbolt lets people unlock doors to homes remotely using smartphones, and features alarms that shriek if incorrect codes are entered too many times.