In early 2005, Firefly Mobile, a privately held cell phone maker based in Lincolnshire, unveiled its enterprising first product: a scaled-down cell phone designed for kids younger than 13. The phone, shaped to fit snugly in a young child’s hand, has only five buttons: pick up, hang up, call Mom, call Dad, and an address book that can hold up to 20 other numbers programmed by the parent and locked by a PIN.

Firefly isn’t the only phone maker focusing on the tantalizing “tween,” marketing lingo for consumers ages 8 to 12. In the U.S. today 70 percent of adults own a cell phone, according to Yankee Group, a Boston-based industry analyst, meaning that every adult who wants a phone probably has one. At the same time, nearly 60 percent of teens own a phone. As carriers become increasingly anxious about finding new customers, tweens represent a vast, untapped opportunity. Parents spent $62 billion on tweens in 2004 for everything from clothes to food to toys, according to Maryland-based Packaged Facts, a figure the company says will grow to $73 billion by 2009. Yet only 10 percent of the age group have cell phones.

But how to persuade young kids and their parents to buy a phone? Samantha Skey, a senior vice president at the New York–based Alloy Media + Marketing, which specializes in the teen and tween market, says the challenge for companies is that tweens want what the older set has. “Tweens are classically aspirational, maybe more so than any other subsegment of the overall young adult population,” she says. “They are very much aware of what the next stage is, and they’re shedding anything babyish”-putting into question the Firefly approach of creating a phone that looks more like a toy than a Razr.

To make matters worse, the Firefly phone is crippled: it dials only preset numbers and does not allow text messaging (often one of the most popular features for kids), downloading of content (music, ring tones), or talking beyond a prepaid limit. And perhaps more damning, parents can program the phone to accept calls from only approved numbers and thus make it hard for users to connect with friends. “This might be like the electronic leash,” says kid-focused product designer Kenneth Jewell of the Boston-based Design Continuum.

But then, the limited functionality isn’t meant to appeal to youngsters, revealing the product’s real target market: parents. According to the company’s CEO, Robin Abrams, the Firefly phone will be used by kids-but controlled by their parents. “The problem that Firefly is solving is that there hasn’t been a mobile phone that met the needs of both kids and parents,” she says. “That’s the innovation-it delivers a level of control over who calls my kid [and] who my kid calls.”

Competitors have the same idea and are rushing to market with products such as the TicTalk; the phone’s address book, calling history, and even allocation of minutes are managed from a Web site by parents, who now can constantly monitor to whom their children talk and how much time they spend doing it. Another cell phone maker, Wherify, expands parental control to a Big Brother-or perhaps a Big Daddy-level. GPS installed in the phone allows parents to look at an online map that pinpoints exactly where their child is and where he’s traveled during the course of the day. Major players such as Disney, Mattel, and Hasbro are all working on kidcentric services or phones. Schaumburg-based Motorola says it, too, is in the early stage of developing a handset for kids.

But the real innovation might just be convincing parents that an eight-year-old should have a cell phone at all, says Michael Wood, vice president of the Northbrook-based Teenage Research Unlimited. “All it’s doing is starting that dialogue at a younger age between kids and parents about having a cell phone,” he says. Of course, that dialogue might end with parents deciding that tweens just don’t need cell phones. And this level of parental control might be too hard for any company to crack.