An accomplished mountain biker is lucky to be alive, with his son crediting his dramatic rescue to an emergency feature on his Apple Watch.

Bob Burdett, from Washington in the United States, was due to meet his son on a trail last Friday.

In the video above: Man miraculously survives cliff fall

However, he never made it to the trail.

He accidentally flipped his bike and was knocked unconscious.

Alone and stranded in the woods, it was an unexpected accessory that saved his life.

Fortunately for Bob, his Apple Watch detected the fall and called emergency services, advising them he was in trouble and where to find him.

By the time his son Gabe had arrived at the scene of the accident, paramedics were already by his side and assisting him.

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Gabe recounted the frightening experience on Facebook while his father recovered in hospital.

"Dad is doing great, clear X-Rays and CT scan, but a little sore for sure," he wrote.

'Amazing technology'

"If you have an Apple Watch, set up your hard fall detection —it's not just for when you fall off a roof or a ladder.

"Had he fallen somewhere on the High Drive trails or another remote area, the location would have clued EMS in on where to find him.

"Amazing technology and so glad he had it!"

Bob was left with lacerations to his forehead after tumbling off his bike. Credit: FACEBOOK

Fall detection is a feature that is built into the Apple Watch Series 4 and Series 5.

It detects when a person has fallen and prompts them to contact emergency services or their pre-set emergency contact.

If it detects no movement after the prompt, it assumes the user is unconscious and contacts emergency services, as well as broadcasting the wearer's location.