Long used by corporate travelers to keep up with e-mail and appointments, smart phones are now catching on with consumers.

Some want to tap out text messages on a QWERTY-style keyboard rather than the tiny keypad of a cell phone. Others see no reason to tote a PDA and a cell phone when a single device can do the jobs of both.

Catering to this growing interest are smart phones that are slimmer and sleeker, with simplified interfaces and setup menus geared toward users who like things fast and easy.

“Smart-phone providers are making a big push into the consumer market,” said Mike Gikas, associate electronics editor at Consumer Reports. “They hope the phones’ advanced features and high-speed-network access will entice users to purchase more services.”

Smart and smarter

For our recent tests of this both-in-one technology, we grouped smart phones into two IQ categories:

¢ What we call “advanced” smart phones offer laptop-like capabilities in a palmtop-sized package. They let you create and edit spreadsheets and text documents, and they usually come with Microsoft Outlook, Palm Desktop or other personal information management (PIM) software for your PC. They typically have touch screens for accessing the phone’s many features.

¢ “Basic” smart phones resemble regular phones, and have fewer features than advanced models. (They typically lack touch screens and PIM software, for example, and don’t allow you to create or edit documents and spreadsheets.) They’re fine for reading e-mail, but composing and sending them is more cumbersome.

A smart phone’s shape and size largely are determined by its keypad and display. Some models have a full keypad that slides out from behind the phone and tucks away when not in use. Others leave the keypads in plain sight, but keys do double and even triple duty. Still others open like an eyeglass case to reveal a full QWERTY keyboard.

Consider system, plans

The kind of smart phone you choose may depend on the operating system it uses.

Smart phones with Windows Mobile 5.0, for example, synchronize easily with Microsoft Outlook on a desktop PC, but are incompatible with non-Microsoft programs.

Palm, the most versatile OS, supports full-featured e-mail and office software programs. It’s the best of the operating systems for basic PDA functions – as long as they’re running one at a time. (The OS gets in the way of multitasking.)

Blackberry is the simplest for e-mail, while Danger is geared toward text messaging.

Found primarily on Nokia phones, Symbian (or Series 60) can be challenging in both its basic and advanced versions.

Using the extra network-dependent capabilities of a smart phone requires both a regular (voice/text) phone plan and a data plan for Web surfing, and sending and receiving e-mail.

Depending on the carrier, prices for both combined start at $45 to $80 a month with a two-year contract. But you easily can spend more than $200 a month as you add minutes, text messages and other services.