Some hotel guests can open doors in a blink

Changing technology has hotels looking beyond the traditional plastic key card as a way to unlock guest-room doors.

The Plaza Hotel in New York, now closed for renovation, will open later this year with radio-frequency cards that unlock the door when swiped past the lock at close range. Paper cards, cellphones, fingerprints and iris scans are popping up as alternative unlocking devices.

The plastic cards that decades ago replaced brass keys still dominate. But the alternative devices could gather momentum as lock suppliers show they can deliver better security, lower costs, greater environmental friendliness or a combination.

The standard plastic key card has a magnetic strip encoded at the front desk to unlock a guest-room door. They cost about 10 cents to make and are designed to be used 20 or more nights.

But guests often carry them away or toss them out after one or two ...