(FORTUNE Magazine) – In a perfect world, we could carry one mobile device--a universal communicator. This device would combine the abilities of a mobile phone, a notebook computer, a contact book, a calendar, a notepad, a digital camera, a digital music player--whew, it's getting really busy, isn't it?--a remote control for your TV and stereo, a voice recorder, a movie and video player, an electronic book, and an e-mail terminal, all with a high-speed connection to the Internet.

The world isn't perfect, of course, but Hewlett-Packard has nevertheless packed all of those features into two new iPAQ handheld computers. They both offer high-speed Wi-Fi wireless networking--the kind you now find at Starbucks and McDonald's and thousands of other hot spots--and that makes them singularly impressive. The catch is, it takes both models to get it all.

One new model, the iPAQ 6315, is the first smart phone I've seen that, along with cellular voice service, includes both Wi-Fi and the slower GPRS (general packet radio service), used for wireless mail and Internet when you're not in a Wi-Fi area. It also has Bluetooth networking, handy for adding a wireless headset.

HP has done an outstanding job integrating all those radios into a package that's relatively sleek and pocket-sized. The key word is "relatively"; it's still too big for my taste, especially compared with my Treo 600 from PalmOne, but it's not significantly larger than its Pocket PC kin.

Marketed exclusively by T-Mobile, the iPAQ 6315 ($499, plus a bucket of voice minutes and unlimited data for less than $100 a month) is a quad-band GSM phone, which means it works not just in North America but also in Europe and other areas.

Handhelds based on the Microsoft Windows Mobile 2003 Pocket PC operating system are great if you keep all your data in Outlook or other Microsoft applications; it's easy to transfer files or contact information between your Windows-based computer and the handheld, and built-in applications like Microsoft's e-book Reader and Media Player are quite handy. However, the Phone Edition of this Pocket PC is poorly integrated, making the iPAQ 6315 more awkward to use than regular cellphones. Heavy talkers may find it frustrating.

Even so, the 6315 is a breakthrough, thanks to its ability to (almost) seamlessly switch between Wi-Fi and GPRS. I was able to browse the web and download mail using the packet radio service, which at 20,000 bits per second (20 kbps) or thereabouts is slightly faster than plucking fragments of information from the air with tweezers, useful only when I'm stuck somewhere without any other access to the web. But when I wander into a Wi-Fi hot spot, the 6315 detects it and turns on the jets, letting me surf or download at speeds of a million bits per second or more, similar to broadband cable or DSL.

The 6315's color screen, slightly smaller than a dollar bill folded in half, is bright and readable even in sunlight, but colors are washed out when viewing photos. (Speaking of photos, HP befouled the 6315's backside with a nasty little VGA-class digital camera, which we'll ignore.) The big screen comes at the cost of a physical keyboard, like the ones on BlackBerries or Treos, essential for poking out lots of e-mail messages and entering data. The 6315 comes with a clip-on keyboard that works well but only adds to the iPAQ's ungainliness, giving it a potbelly.

The other new iPAQ I've been trying is the rx3715 Mobile Media Companion ($499), HP's first handheld for consumers. The rx3715 is designed for play, not work, although it too is a Windows Mobile 2003 Pocket PC handheld with built-in Wi-Fi and Bluetooth. It doesn't have the phone, but it does have a decent 1.2-megapixel Photosmart camera and all sorts of nifty entertainment applications, including a universal remote control and the ability to wirelessly stream music and videos over home Wi-Fi networks to play on network-ready PCs, TVs, and stereos. Still, if music, video, and photos are that important to you, you'll be happier with an iPod, a better camera, and a digital media server: more gizmos, true, but much better quality.

In a perfect world, the HP iPAQ 6315 would have a keyboard implant, liposuction, a transfusion of entertainment features from the rx3715, a wider choice of wireless carriers, and a conversion to the Palm operating system. For now, though, HP and T-Mobile deserve an air kiss for bringing Wi-Fi to a mobile smart phone.