Patrick Newman in Galveston, Texas, knows when his boss is calling--his cellphone plays the theme from The Godfather . Fifteen-year-old Brooke Webster, who lives near Wichita, Kan., uses her camera phone to give friends a sneak peek of her dress for their school's upcoming Hollyball--one of several snapshots she posts daily to the Web. Larry Fortune in Atlanta cut the cord a year ago and joined the millions of Americans who make their calls strictly on cells.

Fifteen years ago, mobile phones were unwieldy and expensive novelties that often couldn't even make a decent voice call. Today they are pocket-size powerhouses that 170 million U.S. subscribers use to take pictures, access the Internet and E-mail, record video clips, and--oh, yeah--call home to make sure they're picking up the right can of soup when they forget the shopping list.

The rush to turn these devices into all-purpose pocket pods will continue as wireless carriers and tech companies roll out flashy new features--services such as tracking your kids' location, top-notch wireless gaming, downloadable TV programs, and audio directions on how to get from point A to point B.

"[The cellphone] is already something you carry with you all the time," says James Burke at Motorola, a leading handset maker. "So it's a great opportunity to meet other needs."

Americans so far have been slower in their embrace of the new wireless services that have swept Europe and Asia--text messaging, for example. There's a lot of uncertainty about which new features consumers really want, says Charles Golvin, a market analyst at Forrester Research. Consumers here want good voice connections, and then maybe wireless headsets and color screens. Surveys by Forrester show that cameras, videocams, and other doodads each right now generate interest in only smaller groups of American users.

But the profit potential almost guarantees that new features will keep coming. Cellphone makers can sell new "mobiles," as they're known just about everywhere except North America, if the devices can do more tricks. The wireless carriers, too, make more money if consumers send more data over their networks. That's crucial to these service providers, who've seen trouble ahead for their profits from voice calls. Stiff competition has slowed growth in voice income, so carriers are throwing everything else at users, hoping something will catch on. "They're in an experimental stage, trying this and that," says Neil Strother, a market analyst at In-Stat/MDR. And the consumer is the guinea pig.

A big hit to date has been ringtones, as cellphone users pay to get their mobile to sound off with favorite tunes whenever someone calls. These services are becoming so popular that Billboard magazine has just started a Top 10 chart for the most popular ringtones. (Last week's No. 1 was "My Boo" by Usher and Alicia Keys.) In Galveston, Newman pays $1 or $2 to download ringers from Verizon for his frequent callers--when it's his sister, who investigates paranormal phenomena, the phone sings out the X-Files theme. His generic ring for others is music from Monday Night Football , even if his beloved Dallas Cowboys are having a rough year. Newman, a medical researcher, says he likes the phone to reflect his tastes, so he's trying to find Irish folk music to load up. More typical is Vincent Trinh, a Houston college student whose phone was recently chiming out Snoop Dogg's "Drop It Like It's Hot" for callers he knew. Teens and young adults are the biggest customers, as they are for the music industry as a whole. Hip-hop--a genre whose digital noises and crisp beats often sound like some electronic alarm anyway--is their choice for ringers. Ringtone quality started at simple one-note-at-a-time melodies, progressed to more complex harmonies of different sounds, and now on some phones can reach radio-quality playback--playing out actual voices rather than digital beeps.

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