The massive blackout of 2003 affected major U.S. and Canadian cities and served as a reminder of the nation's vulnerability.

Some people had to walk down fire stairways in their high-rise office buildings. Meanwhile, firefighters battled several fires that broke out after many people relied on candles for light.

Thankfully, there were few fatalities as a result of the history-making power failure, but now a company has come up with a device that could potentially save lives in similarly dire situations.

Video: LifeCender Aims to Be a Life-Saver

Makers of the LifeCender say it allows trapped occupants of buildings to safely rappel down the sides of buildings to the ground.

Patrick O'Kane, a former high-wire specialist for the Port Authority of New York and New Jersey, got the idea for such a device as he and his co-workers toiled in bucket brigades at Ground Zero searching for survivors.

"I got to thinking, 'How people can get out of fires?'" said O'Kane. "Not just firefighters, but the general public also." 

Using his experience maintaining the microwave tower above the World Trade Center and painting the highest peaks of the George Washington Bridge, O'Kane began experimenting with cords and vests to come up with a descending device.

After a year and a half of research and development, and the formation of a new company, American Escape Systems, the LifeCender was born.

The LifeCender goes on like a life jacket. Made from materials used for seatbelts, parachutes and airbags -- Kevlar and high carbon steel -- the unit can sustain heat upward of 500 degrees and 8,000 pounds of pressure.

"The first question everyone asks is 'What do you anchor to?'" said Bill Henson, CEO and co-founder of AES. The LifeCender can be anchored to any substantial object, like the bottom of a heavy bedpost, or one of three systems that can be purchased with the unit.

"If the door swings inward, we have a spring-loaded door brace," he said. "If it swings outward, we have a bell anchor that hits the door and the floor at a 45 degree angle, dividing the weight equally between the floor and the door. Thirdly, we have a closet anchor that you secure to beams in the corner of your closet."

Once the unit is on and anchored, users can control their descent with a knob that monitors the speed at which the cord is unspooled. Users can either go down hands-free, kicking off the side of the house or building, or by walking down the building with their hands like Spider-Man.

Currently, the technology allows for descents of up to 7 stories.

Some consumers like Jennifer Suzanne from Petaluma, Calif. said they'd be wary of rappelling out a window in an emergency, but would be glad to have some alternative.

“I guess if that were my old way out, I’d be happy to have it,” said the 33-year-old. “But I might be a little nervous to use something like that, especially from the seventh story.”

"What it does is give civilians a way to escape from a burning building before a firefighter has to risk his or her life trying to save them," said Paul Hashegan, a retired FDNY firefighter. "When I go on vacation I'm just a civilian, and I usually carry a rope with me. Now I'm going to carry a LifeCender."

The LifeCender comes in small, medium and large and holds people who weigh up to 300 pounds. It's a one-time use device, meaning after the cord is unwound it can't be sent back up for another user.

"It's not a toy," said O'Kane. "With a police and fire report, we will replace the unit free of charge for life. You can't put a price on a life."

But you can put a price on the unit. It starts at $189 and goes up to $289.

As for O'Kane, who has given up his job with the Port Authority to help develop and market the LifeCender, he said he just hopes the invention can improve fire safety. 

"The first day that it saves someone's life it'll all be worth it."

The LifeCender was recently featured on FOX Magazine, on FOX News Channel.