Matt Ruddell, whose former partner Tracey O'Brien died a fortnight ago in a crash that also hospitalised his two children, says people need to learn to "divorce" their phones.
The 27-year-old, pictured, who has spent the past two weeks in Starship children's hospital with his kids, said the loss of his children's mum had been a "wake-up call" for him to get off his phone in the car.
He hoped others wouldn't need to suffer a similar loss to understand the importance of ditching the cellphone.
"Is the call or the one text message really worth it? Is it worth what we're going through?
"It's just been a massive wake-up call ... Just divorce your phone. If there's a call and it's that important, pull over," he said.
Ms O'Brien, 26, died when her car crossed the centre line outside the Charlemagne Lodge wedding venue in Te Puna, near Tauranga.
Three-year-old daughter Faith and 4-year-old son Phoenix survived and are now out of the high dependency unit and in a ward together.
Police have said the early indications are that she was using her phone.
When told about the driver smoking a cigarette and talking on his phone, Mr Ruddell was amazed: "If you've got your hands full and you're trying to drive, that's beyond ridiculous."
He has admitted to using his phone while driving in the past, but said he now left it on the floor on the passenger side of the car.
He now texts before he leaves, rather than en route, he said, and has been encouraging friends and family to do likewise.