Seattle officials say the rescue shows the potential a free download has for connecting CPR-trained citizens with patients who urgently need their help. It's being used in 2,000 U.S. cities in 28 states.
"I put it on my phone yesterday," said DeMont's wife, Debi Quirk, a former registered nurse. "He would not be here as we see him today."
Seattle officials hope DeMont's story will help persuade thousands more people to sign up for notifications; so far, about 4,000 people in Seattle have downloaded PulsePoint since the city adopted it earlier this year with financial support from an employee charitable fund at Boeing. The goal is to have 15,000 using it.
The app, which works through a city's 911 system, was developed by Richard Price, the former chief of the San Ramon Valley Fire Protection District in Northern California. When a call comes in, operators alert people within a certain radius that CPR assistance is needed, along with the location of the nearest portable defibrillator.
About 900,000 people around the country have downloaded and carry the app, and 34,000 people have been activated to respond, Price said, adding that alerts have been issued in 13,000 cardiac events.
He came up with the idea in 2009. Price told KQED in a 2011 interview that he'd been eating lunch in a deli with three colleagues, when "we heard a siren, and we were wondering where the guys were going. They parked right in front of the deli we were eating at."
As it turned out, an unconscious patient close by was in need of help.
"Here's the fire chief in uniform, a defibrillator in my car. One of my [lunch companions] is a paramedic, and right next door to us, someone was in great need and we were completely unaware of it.
"We sat the the rest of the afternoon and diagrammed on deli napkins how we could make sure that never happened again."
In that 2011 interview, Price said survival rates for those in cardiac arrest are very high when CPR is used within the first 2-3 minutes after cardiac arrest.
It's not clear how many lives have been saved thanks to the app. Patient confidentiality laws often prevent hospitals from disclosing a patient's outcome.
Madeline Dahl, a 23-year-old cardiac nurse at the University of Washington Medical Center, said she downloaded the app about a month ago after reading a news story that mentioned it. Last Friday morning was the first time she'd ever received an alert. She bolted down a couple flights of stairs and ran outside into the rain, where she found 27-year-old medical student Zach Forcade performing chest compressions.
Forcade had been on his way into the hospital for a lecture when he saw DeMont, who was just getting off his bicycle, slump over.
"I hadn't responded to a cardiac arrest before," Forcade said. "I thought, 'Did he just fall?' ... Even being in the medical field, I thought, 'Oh, man, who's going to step up?'"
He told another passerby to call 911, which triggered an alert sent out to 41 responders nearby. It was reassuring when Dahl arrived to provide any needed backup, help check for a pulse and otherwise make sure Forcade was responding correctly, he said.
For DeMont, it was about more than just being lucky. A contract technical writer at Expedia, he said he has a love-hate relationship with technology — "You see all these things about people falling off cliffs texting, people are so disconnected" — but the response from Forcade, Dahl and the use of PulsePoint reaffirmed his belief in its power to make a positive difference.
"There's hope," DeMont said.
He's due to have a defibrillator implanted on Thursday. Now he just has to figure out how to pay the $100,000 tab without insurance.
For that, his family has turned to a program with a different app: GoFundMe.