To further poke holes in the article:

Sylvan, 14, has several after-school activities and lets his parents know when he's going to be late.
He'll be on time or walking home, his choice.

Alana, 10, who just moved to a new neighborhood, calls home when she's not sure about directions.
What's a 10 year old girl doing walking around a new neighborhood without supervision?

Josh, 11, whose parents both work, lets them know when he gets home from school.
While there is no set guideline in most states for the age for a child to be left home alone, 11 is too young in my book, anyway. Maybe the parents need to find jobs on opposite shifts?

The article post a lot of generalities, provides specious reasoning for a child to have a cell phone, and cites no supporting data.

For an article written by a PhD, it shows an amazing lack of substance or reason.