Given that the vast majority of grown-ups who might need one are already surgically attached to their cell phones, where are the device makers and wireless service providers going to turn for future growth?

All you parents of young children need to gather round for this one. We're talking about the "tween" market, or those youngsters ages 8 through 12. . . . Yes, really.

"The tween market is currently under-penetrated compared to the overall population," writes Yankee Group analyst Marina Amoroso in a recent report intended to help vendors fix this, um, problem. "Despite a number of important challenges, it represents one of the key growth opportunities for the wireless industry."

We'll get to the challenges in a moment.

Yes, I was already aware that a teenager without a cell phone is like, duh. I've seen the TV commercials for the kiddie phones. Yet this father of three 4-year-olds was simply unprepared to grasp the idea that my little tykes might be packing their own cell phones in only a few years; or in other words, before they can reliably pack their own lunches.

Silly me.

According to Amoroso's report, 27% of tweens are already gobbling up those minutes on Mom and Dad's dime, with that number expected to double by 2010. And while 8-year-olds naturally make up the smallest slice of the tween market segment, their numbers are still astonishingly measurable, as in almost one out of every 10 today.

Fueling the trend are a combination of mass insanity and family-share plans that make adding your 8-year-old a relatively painless $10-a-month decision - provided you don't have triplets.

Yet obstacles do remain that are preventing vendors from making even deeper inroads into the Little League set, according to Amoroso. Parental controls on some models are not robust or easy enough to use, although Web-based versions are addressing those weaknesses. And the phones themselves just aren't being built to suit the intended audience.

"What we expect is that they're finally going to recognize that an 8-year-old's mind-set and aspirational age is completely different than that of a 10-year-old," Amoroso says. "And what they think is cool or cute is completely different, as well."

Which, unless I'm not following along here, means your 8-year-old will require an upgrade when he hits 10. Notice I said yours, not mine.