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ABC News' Paula Faris reports:

A car belonging to uber-trainers Chris Powell and his wife Heidi of ABC's "Extreme Makeover Weight Loss Edition" was carjacked in Mesa, Arizona while being driven by their nanny, who had the couple's one-year-old son inside.

The couple's toddler Cash and Kaitlyn, the couple's nanny, were in the backseat of the Buick Enclave when a man approached.

"He said get out of the car or I'll kill you and the baby," Heidi said. "Luckily she remembered to grab the baby, because in that situation, who's to say what you remember to do and don't remember to do."

The suspect drove off, but technology would ultimately be his undoing when police used tracking software to locate and disable the vehicle.

Chris Powell told "Good Morning America" Tuesday that he was in Milwaukee when the carjacking happened, but was on the phone with Heidi when Kaitlyn came rushing into their home.

"I heard our nanny Kaitlyn come running through door screaming, 'He's going to kill me, he's going to kill me and the baby!' As you can imagine, I'm thinking 'what the heck is going on?'" he said. "I hear Heidi calm her down … and as I heard the details, I started to panic because it was such a helpless feeling for me, being thousands of miles away."

Powell said that they then called the police and in-vehicle security company OnStar, and got the wheels into motion to retrieve the car and apprehend the criminal.

"They tracked the car. It wasn't more than 2.5 miles away," Heidi said. "They were able to stop the criminal, stop him dead in his tracks in the car. He hopped out by foot."

The carjacker had also grabbed Heidi's iPad when he fled the car. Fortunately, there's an app for that too. Heidi and police used the Find My iPad application, and within half an hour, officers had the suspect in custody.

Jasper Stewart, 32, was arrested on robbery charges. According to ABC15, he is a documented member of the Nazi Low Rider gang.

A grateful Powell tweeted on September 7: "Our nanny is so amazing. She quickly responded and got Cash to safety. She is a rock star hero."

Heidi says she is very relieved that the incident is behind all of them.

"Cash is safe, Kaitlyn is safe." she said. "We got our car back which I didn't care about and had written off. I feel so grateful and lucky.

Powell told "GMA" that he does not believe that the celebrity couple's car was specifically targeted. He thanked the police who helped in the situation and recommended that people be more aware of what's going on around them.