Labour's costing show the capital cost of the policy would be $11 million in 2015/16 and $12 million the year after that - although it will also look for private partners to help finance the costs of the devices.
The operating cost is expected to be $19 million in its first year, rising to $41 in 2016/16 and $26 million in 2017/18, including the kickstart payments, hardship fund and provision to write off or chase up debt.
The devices would be new and fully insured.
Mr Cunliffe also said he stood by saying he was sorry for being a man yesterday, after the comment attracted ridicule.
Read more: Cunliffe: 'I'm sorry for being a man'
He made the comments at a Women's Refuge forum in Auckland where he said he's sorry that he's a man because men commit most family violence.
"Can I begin by saying I'm sorry," he said.
"I don't often say it. I'm sorry for being a man right now, because family and sexual violence is perpetrated overwhelmingly by men against women and children.
"So the first message to the men out there is: wake up, stand up and man up and stop this bull****!"
On The Nation this morning, Mr Cunliffe said he was proud to be a non-violent man, however no one should be proud of the country's domestic violence statistics.
"Yesterday the message was all about Labour's policy against domestic violence, we've lead that debate and I've stuck my neck out on this.
"I wrote that, and I stand by every word of it."
Mr Key said Mr Cunliffe's comments were insulting to New Zealand men.
"The problem isn't being a man, the problem is if you're an abusive man. I think it's a bit insulting to imply that all men are abusive.
"A small group are, and they need to change their behaviour and be held to account."
Mr Key questioned whether the Labour leader was sincere about the statement.
"Is he going to go down to the local rugby club and get up and say 'I'm sorry for being a man'? I don't think so."