THE bedroom door opened and a light went on, signaling an end to nap time. The toddler, tousle-haired and sleepy-eyed, clambered to a wobbly stand in his crib. He smiled, reached out to his father, and uttered what is fast becoming the cry of his generation: “iPhone!”

The iPhone has revolutionized telecommunications. It has also become the most effective tool in human history to mollify a fussy toddler, much to the delight of parents reveling in their newfound freedom to have a conversation in a restaurant or roam the supermarket aisles in peace. But just as adults have a hard time putting down their iPhones, so the device is now the Toy of Choice  akin to a treasured stuffed animal  for many 1-, 2- and 3-year-olds. It’s a phenomenon that is attracting the attention and concern of some childhood development specialists.

Natasha Sykes, a mother of two in Atlanta, remembers the first time her daughter, Kelsey, now 3 1/2 but then barely 2 years old, held her husband’s iPhone. “She pressed the button and it lit up. I just remember her eyes. It was like ‘Whoa!’ ”

The parents were charmed by their daughter’s fascination. But then, said Ms. Sykes (herself a BlackBerry user), “She got serious about the phone.”