He continued with the abusive texts, saying he would be over that night and would cut her head off.
He referred several times to the victim being dead, said he would have her bleeding on their son before police arrived, and that he would stitch their son into her stomach.
Defence lawyer Frank Minehan said Peachey has been attending a stopping violence course and would be willing to offer an emotional harm payment to the victim.
He said Peachey had shown a degree of remorse.
Judge Jill Moss said she was unsure whether Peachey had worked out that his plan to try and hold his former partner in the relationship, by making her fearful, was "a really dumb thing".
"You don't want to teach your baby that this is the way to live your life.
It's all about what the future for your baby looks like," Judge Moss said.
Judge Moss sentenced Peachey to six months' supervision and ordered him to pay the victim emotional harm reparation of $300.
On a charge of wilful damage to the victim's car, Peachey was convicted and discharged.