COLUMBUS, Ohio — When Anna- marie Saarinen needed to soothe her ailing daughter, she used a rattle — downloaded to her iPhone.
Jeff Hilimire uses a white noise application on his phone to make shushing noises for his infant daughter. And Tracie Stier-Johnson lets her young daughters answer trivia questions on her phone while waiting in the doctor's office or at parent-teacher conferences.
"You can only play 'I Spy' so many times," said Stier-Johnson, 40, of Racine, Wis., whose daughters like the "Who Wants to be a Millionaire" game she loaded on her iPhone.
Parents have handed their cell phones to children as distractions since they were invented, and toy versions tap into kids' love of pushing beeping buttons and playing with electronic gadgets like the ones their parents have. But a mushrooming number of applications on smartphones have parents using them more than ever as modern baby rattles.
These wired-up phones allow parents to play number and letter games with their preschoolers or to get a few minutes of quiet when children watch movie clips on a plane or while waiting for a restaurant table.
Jenny Reeves, 34, of San Antonio, lets her boys, ages 3 1/2 and 2, type words or flip through pictures of themselves and their dog on her BlackBerry when they have to pass time without books. Her older son is learning to send e-mails to his grandparents and dad that say, "I love you."
"It's almost as good as lollipops," Reeves said.
People also are making their phones parenting helpers, downloading applications to turn them into impromptu baby monitors, to research nutrition information in grocery aisles and to check their babies' growth rate compared with average measurements.
Hilimire, a 33-year-old father from Atlanta, started putting his iPhone to work before his daughter was born, when he timed contractions with the phone's stopwatch and downloaded software that showed the size of the growing baby.
Now when his infant daughter gets fussy in the car or during a walk, he puts his iPhone in her carrier to play the free application called White Noise Lite. "It immediately relaxes her," he said.
Stier-Johnson leaves her iPhone near her sleeping 3-year-old daughter to listen for her to wake when she sits near her pool, which is out of range for her regular baby monitor. An application she downloaded prompts her phone to call her home number or her husband's iPhone when her daughter makes a noise.
And the phones have been put to work in times of crisis, too. Saarinen and her husband, Paul, of Minneapolis used a program called Cardio Calc on his iPhone to track infant daughter Eve's health information during a recent stay in a Boston hospital for heart surgery to repair problems including a leaking valve.
A free rattle application, Baby Rattle Bab Bab Lite, showed spinning graphics and chimes when Eve moved it around. It stopped her most intense crying when she was coming off pain medication, Annamarie said.
Smartphones can be an expensive child diversion, to be sure. Some parents set rules for kids to try to prevent damage, such as no shaking and no carrying the phone on hard surfaces in case it's dropped.
And some have trouble keeping their phones away from the children or worry about limiting phone time once the children move into elementary school.
Brooks Duncan of Vancouver, British Columbia, has to hide his iPod touch from his 2-year-old. "If he sees it, he'll go for it and want to play with it," said Duncan, 35, who bought the device when his children started arguing over their grandfather's iPhone.
Sascha Seegan, lead mobile device analyst for PCMag's network of Web sites, said a good chunk of available apps is useless. Apple's App Store has 35,000 applications for iPhone and iPod touch. Handango.com sells 140,000 titles for various phone brands, and a couple of hundred of those are aimed at parents and young children, said Alex Bloom, president and chief executive officer.
Seegan suggests reading user ratings online and professional reviews, along with checking that all the application's features work smoothly and quickly. But he doesn't let his daughter, now 3, play with the phone yet.
"Maybe I'm just paranoid, but I wouldn't use a $300 baby rattle," he said.
Still, other parents are stunned, and impressed, when their toddlers quickly figure out how to operate the phones, sometimes faster than their moms and dads.
When Byron Turner left his new iPhone alone with his 4 1/2-year-old twin boys for 25 minutes, they had figured out what many of the phone's touch-screen buttons did and started taking photos. The boys, now 6, have improved their spelling with a hangman game and use an application that makes their parents' phones sound like lightsabers, said Turner, 46, of Grass Valley, Calif.
Duncan said his children can find what they want by browsing through icons.
"To be able to do that before you're 4 years old, just think what they're going to do," he said.