Dan Pfau, a retired management consultant from Newton, is back at his vacation home on Martha’s Vineyard. I’m not sure that’s such a good idea, considering how many times his visits have ended in the emergency room. But Pfau is wearing his Apple Watch, so he’ll probably be OK.

Pfau, 70, belongs to a fairly exclusive club that few of us would want to join — people whose smart watches may have kept them alive. Indeed, Pfau says it’s happened twice.

Nowadays the tech giants are under fire for all sorts of transgressions, and we’ve begun to take our gadgets for granted. But it’s good to be reminded of their almost magical power, and their continuing capacity to reshape our lives, and possibly even save them.

Pfau was first rescued by his watch about two years ago during a Martha’s Vineyard cycling excursion.

“I turned onto a lightly traveled road that turned out to have speed bumps,’’ said Pfau. He believes it was one of these that knocked him off his pedals, but he doesn’t recall the impact.

“The next thing I remember was waking up in the ambulance,’’ he said.

Pfau doesn’t even recall phoning 911, because he didn’t. The watch did. In 2018, Apple added a feature that can tell if the user has fallen down. If the user doesn’t move for 60 seconds, the watch puts in a call for assistance. (The technology involved is similar to what Google highlighted this year in a TV ad about its Pixel phone detecting that a user was in a car crash.)

According to Pfau, the emergency room doctors found a hemorrhage in his brain. “They actually helicoptered me to Mass. General,’’ he said. Happily, the doctors in Boston discovered that it was a minor injury that healed on its own. But that was the end of Pfau’s cycling career: “My cardiologist said no more riding bikes.’’

The injury wasn’t quite as bad as it first seemed, but Pfau believes that’s because the Apple Watch was so quick to call for help. “I don’t know if I would have died otherwise,’’ he said, “but it certainly would have been more serious.’’

The second incident, which happened just last month, was even scarier.

“I have a history of fainting,’’ said Pfau, and on a recent morning that’s exactly what he did. “I hit my head on the hardwood floor and I started bleeding significantly,’’ he recalled.

Pfau woozily staggered to his feet, stumbled to the bathroom, and fell again. He was barely conscious, unable to move. And his neck began to hurt.

His Apple Watch didn’t dial 911 this time, because Pfau, still conscious, tapped an icon on the watch screen to indicate he was OK. “I assumed it was not that serious, which is my natural reaction,’’ he said. But when he realized that he wasn’t OK after all, Pfau launched the watch’s texting app, tapped the microphone icon, and dictated a message to his wife, who was downstairs.

It took nine stitches to close the cut on Pfau’s forehead, but the pain in his neck sentenced him to four days in intensive care — it was a fractured vertebrae. “The doctors said I was extremely lucky not to have paralysis,’’ he said.

Pfau wound up at Mass. General after another helicopter ride. “My wife cracked that I was trying to rack up helicopter frequent flyer miles,’’ he said.

Brad Weiner, Pfau’s primary care physician, wasn’t around for the cycling accident. But he confirms the story of Pfau’s more recent close call. And it’s not the only time one of his patients has hailed a smart watch as a lifesaver.

“I had another patient just last week whose Apple Watch correctly told him he was in atrial fibrillation,’’ Weiner said.

AFib, as it’s called, is an irregular heartbeat that can signal serious cardiac problems. The heart rate sensor on the Apple Watch can alert a user before it’s too late.

Pfau doesn’t love everything about his Apple Watch. “I have nicer-looking regular watches,’’ he said. But what have those other watches done for him lately? Given his remarkable run of luck with the smart watch, Pfau said “it would be foolish not to wear it.’’

Apple Watch isn’t the only brand credited with lifesaving powers.

Fitbit, the Google-owned maker of fitness-oriented smart watches, has several similar anecdotes, like the case of a college professor whose Fitbit showed a dangerously high heart rate.

A trip to his doctor resulted in emergency surgery to repair a blood vessel obstruction that could easily have killed him.

For privacy buffs like me, there’s still something unnerving about a life under constant digital surveillance. But for survivors like Daniel Pfau, it beats the alternative.

Hiawatha Bray can be reached at hiawatha.bray@globe.com. Follow him on Twitter @GlobeTechLab.