PHOTO: Helio

Helio Ocean: Service: Helio; Coverage: New York City—excellent; Cedarville, Mich.—poor; Keyboard: QWERTY

Instant messaging has been a major desktop application for a decade. But it’s potentially even better when you’re on the go, which is why wireless carriers in the United States are beginning to offer it.

It’s clear why customers would sometimes prefer IM to text ­messaging. Besides the back-and-forth dialogue format, you get to pick your contact from a short list of buddies instead of the longer one for all your contacts. Best of all, the buddy list shows who’s online and whether they’re available, a feature called “presence.” Such information is already built into some corporate e-mail ­applications, and it’s clear it will ­eventually make its way to all cellphones.

To find out how well IM works on a tiny cellphone, I put three new and very different phones and their ­respective carriers through their paces, and as a further stress test, I shipped them off to a friend in Michigan’s Upper Peninsula, where service can be spotty. All the phones come from Asia or are of mixed Asian-European lineage, which is interesting because IM is more important in the United States than anywhere else.

The Ocean from Helio, a cellular service that launched in May, has a distinctive double-slider design: it opens ­vertically to expose a ­typical 12‑key phone ­keypad and ­horizontally to offer a QWERTY thumb keyboard. The result is a phone as heavy and bulky as any PDA, but even more useful. With more time, I would have explored the Ocean’s corporate e-mail ­capabilities and its many multimedia options, among them the ability to upload ­photos directly to a MySpace page.

PHOTO: Sony Ericsson

Sony Ericsson W580i: Service:AT&T; Coverage: excellent; Keyboard: standard 12-key

The new Sony Ericsson W580i is one of only a few in AT&T’s lineup to offer IM (for an additional US $5.99 a month). It’s compact and ­stylish, and substantial without being heavy. It, too, has a slider design, but with only a standard 12-key keypad. As befits the Sony name, it offers ­several music options, including an $8.99 ­streaming music service called MobiRadio. (My first song on the classic rock channel was Neil Young’s “Southern Man.” It’s hard to argue with that.)

PHOTO: samsung

Samsung Blast: Service: T-Mobile; Coverage: New York City—good; Cedarville, Mich.—adequate; Keyboard: unique 20-key

The Samsung Blast is ­lightweight, which isn’t all to the good, because it feels flimsy. The slider reveals a keyboard that Samsung is very proud of. The 20 keys each bear only two ­letters, laid out QWERTY fashion, so that instead of having “ABC” under the 2 and “PQRS” under the 7, the uppermost-leftmost key has “QW,” the next one over has “ER,” and the one below it has “AS.” This design can save a great number of keystrokes, but only after you’ve spent the time it takes to get used to it.

Conspicuous for its absence is Apple’s iPhone, which lacks IM ­service even though its exclusive service ­provider is AT&T. Why AT&T would give IM capability to lesser phones but not to the single most prominent and Internet-friendly phone in the world is anybody’s guess.

So how do the three stack up?

Considered purely as an appliance, the Ocean is clearly the best. It makes it easy to find and use every feature of IM—status, multiple conversations, ignore lists, and so on. It even showed my different buddy categories and let me sort by online status. I could view, or not view, offline contacts. I used the Yahoo application, but the phone also offers AOL and Windows Live.

Unfortunately, IM on the Ocean, which runs on Sprint’s cellular ­network, stands or falls with the ­wireless service. That turns out to be far less than the seamless nationwide coverage that Helio promises. There was no service at all in and around Cedarville, Mich., according to Janet Haske, the technology coordinator for the local school district there and an inveterate IM user. When Haske went downstate, to Mount Pleasant, Mich., she found that even there the ­coverage was spotty at best. “I can see how this phone, with its nice keyboard and large display, would be good for text functions, but with no reception, none of this matters.”

Haske was also less than thrilled with the Samsung Blast. “The display was hard to see in bright light, and I absolutely hated the ­keypad, which was very difficult to use. I’m sure I’d pick it up eventually, but for the amount of time I had it, I was ­frustrated.” She found its ­connectivity to be “a ­little on the slow side.” I, too, found it took longer to log in with the Blast than with the other phones. In addition, when I superseded my phone log-in by logging in on my desktop, the Blast didn’t note that it had been logged out. On the upside, it offers even more IM applications than the Ocean.

Haske greatly preferred the Sony Ericsson phone. “Reception was great everywhere I went, even in the northern­most regions of Michigan,” she said. “It’s slim, easy to handle, and the keypad had a nice layout that was good for my small hands.” Haske also lent the phones to her son and several of his friends when they visited her one evening: “It was the favorite of the 20-something crowd.” I also liked the W580i. One downside: it carries only one instant messaging service, Yahoo’s.

As is so often the case with new applications, none of the ­available choices is perfect. As Haske put it: “Ultimately, I want a phone that will remotely start the washing machine and coffee pot and track my ­significant other’s Internet ­habits. Is there one out there like that?”