For a month, I toted around Vodafone’s 905SH, manufactured by Japan’s Sharp. It sported a stainless steel frame and a striking black 2.6-inch LCD screen, which swiveled 90 degrees to display nine channels of digital television in crisp, widescreen format. It also surfed the Web, served as a debit card, downloaded and played music and took two-megapixel photos. It won my heart. Here in America’s pokey mobile-phone market, we have nothing like it.

Thanks to early investments in high-speed mobile networks, Japan’s cellular telephone industry is about a year and a half ahead of America’s. Everywhere you look, it shows. Subway riders tap messages to friends, listen to music and play games on their handsets. More than half of Japan’s cell-phone users own speedy 3G broadband phones (versus a puny 5 percent in the United States). Advertisements for an even cooler wave of new handsets now adorn public billboards, in advance of new “number portability” rules coming this fall. The regulations will make it possible for users to keep their numbers when changing wireless services—in effect intensifying competition between the three major mobile carriers and forcing them to innovate. The phones are about to get even cooler.

Yet even now, it’s a treat for any deprived Westerner to carry around one of these stocked multimedia devices. My 905SH was a beauty. The Japanese have enjoyed analog TV on their mobile phones since 2003, but the quality was erratic and users would lose the signal on moving trains. Earlier this year, the carriers unveiled a new digital TV standard, devised solely for mobile devices. The quality is excellent. My phone not only played seamless television but let me record, TiVo-style, up to five hours of TV on a one-gigabyte memory card. I could study Japanese television shows as many times as I liked. I watched Yomiuri Giants games and the first Christopher Reeves “Superman” in Japanese.

The phone was also my personal entertainment companion. I wasn’t actually going to talk on the thing in subways and cafes—in Japan, that’s considered rude, as signs and public announcements amply remind you. Instead, I played games like the realistic 2006 Real Soccer, surfed the Web and downloaded Japanese manga (comics).

When I wanted to give my tired fingers a rest, I relaxed and listened to music. In Japan, 90 percent of all downloaded songs are enjoyed on mobile phones, rather than to PC-tethered devices like the iPod. I followed along, downloading the J-pop hit “Super Sonic” from singer Koda Kumi for 262 yen ($2.26) from the mobile music store Chaku Uta, and made it my ringtone.

I caught a particularly compelling glimpse of the future by using the phone to replace to my bank card. Vodafone allows subscribers to use a national electronic cash network called Edy. I downloaded the software to the phone and easily got a cashier to add $10 to it at a local supermarket. Then I went a spending spree, waving the handset near the Edy reader next in a café to buy coffee and a pastry. It automatically deducted money from my account. Thousands of stores, vending machines, train stations and taxicabs accept e-money in Japan—and the mobile carriers will soon add a credit-card function, so you can buy now, pay later and leave your wallet at home.

The one area where my beloved phone fell short was GPS navigation. Unlike a majority of new Japanese phones, Vodafone’s 905SH doesn’t have a GPS chip or mapping software to help users negotiate the baffling geography of Japan’s cities. I nevertheless got to try out that feature while utterly lost one day in Tokyo’s Ikebukuro entertainment district. As we set out for dinner, our friend Patrick whistled up the “ez navi” GPS software on his AU phone and tapped in the coordinates of the restaurant where we had reservations. Holding up the phone like a “Star Trek” tricorder, we walked past the incomprehensible street signs, following the blinking green line on the screen to our destination. Captain Kirk would be proud.

Japan’s advanced wireless ecosystem is now poised to get even better. The country has three major cell-phone carriers: leader DoCoMo, which has 56 percent market share; rising player KDDI, whose AU service has 28 percent, and the local arm of Britain’s Vodafone at 17 percent, which local Internet firm Softbank purchased earlier this year and will rename Softbank Mobile. With new number-portability rules set to take effect on Oct. 24, analysts think as many as 5 million to 10 million Japanese phone users might switch carriers.

So the three companies are fiercely trying to entice their customers to stay and lure new users from their rivals. Prices are dropping, new handsets are coming and the carriers are upgrading networks with even faster 3G technology. New applications on the horizon include video calls, biometric authentication (using your fingerprint to authorize phone purchases) and handsets that remotely program home electronics and open locked doors. Automobile-trapped, PC-addicted American’s haven’t shown nearly as much interest in these kinds of advanced mobile-phone applications. So there’s no telling when, or if, these futuristic features will ever make it across the ocean.

In Japan, the only tragedy is that my beloved Vodafone 905SH will soon be obsolete. Perhaps it’s best. If I can’t have her, no one can.