When doctor Andrew Crellin collapsed at home in the dead of night his family rang Triple-0, and a PJ-clad hero arrived at their door.

Off-duty Ballarat paramedic Jess Handley lives nearby, and had been sleeping, but was alerted to the emergency by an Australian-first Good Samaritan app.

“I didn’t even take the time to get out of my pyjamas - I just threw on a hoodie and went down to Andrew’s house,” Jess told 9News.

Off-duty paramedic Jess Handley got an alert on the ‘GoodSAM’ app when doctor Andrew Crellin went into cardiac arrest in his home nearby. (9News)

Dubbed “GoodSAM”, when an ambulance is dispatched for cardiac arrest the good Samaritan app also sends a medical mayday to people nearby who have first-aid training.

That bystander can then race to the scene and administer first aid while emergency services are on the way.

“We are just very grateful to have had Jess arrive at the time she did,” Andrew told 9News.

The 49-year-old, who is also an emergency doctor, didn’t have a pulse when Jess arrived, so her quick response saved his life.

Victorian Health Minister Jenny Mikakos says the GoodSAM technology has already proved a success, helping revive 20 cardiac arrest victims in the past year.

When an ambulance is dispatched for cardiac arrest the good Samaritan app also sends a medical mayday to people nearby who have first-aid training. (9News)

“It is reassuring to know that you may have your neighbour or someone in your apartment building potentially come to your assistance when you need them most,” Minister Mikakos told 9News.

When it launched last year, the GoodSAM program had been restricted to health and emergency professionals such off-duty paramedics, nurses or firefighters.

Today the State Government joined Ambulance Victoria CEO Tony Walker to announce anyone with recognised First Aid Training can now become a first responder volunteer.

“Those first few minutes when someone is performing CPR can make a world of difference,” Tony Walker told 9News.

“Those first few minutes can make a world of difference.”