The baby monitor showed Stacey Gleeson that her 1-year-old daughter Giana had turned blue.
She went to her and discovered she'd stopped breathing.
The mom from Cairns, Australia, told 7 News that she picked up her daughter and checked her airways. Then: "I looked over and remembered my phone."
Before the ambulance had arrived Giana's mom had got her breathing again.
However, Giana's dad Nic told 7 News that the fact that mom didn't have to leave her child to make the call may have made all the difference.
Apple didn't immediately respond to a request for comment.
Cupertino has recently been heavily advertising the "Hey, Siri" function, even hiring the Cookie Monster as a spokesman.
It seems, though, that Siri use is far more prevalent in cars and homes, as people still feel uncomfortable using voice assistants in public.
In cases such as Gleeson's, when a mom is alone with her child, it can be that Siri is a vital help.
Mom says Giana has made a full recovery.
This article originally appeared on CNET.com.