Keen cyclist Bruce Mildenhall does not remember being knocked off his bike or an off-duty paramedic treating him before an ambulance arrived.
He simply recalls the moment he woke inside the vehicle on a stretcher, being treated for serious injuries while his wife knocked on its window, calling his name.
That's the tale he tells in one of two short films tech giant Apple will launch on Friday to demonstrate how smartwatch technology has helped to save lives.
And an expert says the two cases are not isolated incidents, with advanced sensors and improved data making it easier to track users' health and alert them to ailments.
Mr Mildenhall, who was riding his bike around Mt Macedon in Victoria before the accident, said his new Apple Watch alerted his emergency contacts following his accident, at a time he could not do it himself.
"A kangaroo had jumped out from the forest... and smashed into the side of my bike and I'd gone face over apex and landed on my head and smashed my shoulder, crushed vertebrae, broken ribs, all sorts of things," he said.
"But the watch had obviously detected the hard fall and sent an SMS to my wife to say Bruce has had a hard fall, hasn't responded and this is where he is, and also dialled emergency services."
In addition to Mr Mildenhall's story, Apple will launch a short film featuring Lexie Northcott, who was just 17 years old when she told her doctor about persistent low heart rate alerts from her smartwatch.
After initially dismissing the concerns due to her age and fitness, her doctor ordered an electrocardiogram.
"We got brought into a room with three different doctors and they told me straight up that I had a complete heart block," she said.
"Within five days, I had a pacemaker implanted."
Her mother, Karla, said one of the scariest parts of the experience was no one suspected Lexie could be ill.
"She had no indications that she had a heart problem at all," Ms Northcott said.
"I just get chills whenever I think, imagine if she didn't have that watch because I believe she would not be here now."
Apple's smartwatches include features such as fall and crash detection, low and high heart-rate notifications, and alerts for irregular heart rhythms.
Smartwatches from other companies including Samsung, Google, Fitbit and Withings also use sensors to track vital signs such as a user's temperature, blood oxygen, heart rhythm, stress level, and sleep quality.
University of Sydney Assistant Professor Omid Kavehei said packing health sensors into devices such as watches, rings and spectacles made vital signs easy to track over a period of time, helping to alert wearers to potentially concerning trends.
He said the growing number and sophistication of the sensors could help medical professionals identify more issues than they had before.
"The more sensors you have, you get more complementary or auxiliary data that help you make a diagnosis with a higher degree of confidence," he said.
"It is getting to a point where they are capable of very, very robust demonstration."
Medical studies have used wearable devices to investigate issues including sleep apnoea, epilepsy, heart disease, and sleep trends.
