With a wireless personal digital assistant, you can be in constant contact on the road

There are challenges to being a mobile manager. Sometimes you have to get an E-mail message while you're in transit, before you get to your meeting. Or sometimes you need information from a database that's in your office when you're at a customer's site.

If you've ever pined for instant communication while you were away from a phone jack, you know that pagers work well when paired with cellular phones and that laptops with cellular modems are good for checking your E-mail now and then. But if you want to be in contact more regularly and easily, you need something more--something wireless.

Two very portable personal digital assistants (PDAs) are being targeted toward the consumer who demands both small size and wireless-communication capability. The Motorola Envoy 150 Wireless Communicator (800-894-7353; $875 to $1,175) is a machine with a built-in wireless modem. The MessagePad 130 with Newton 2.0 Operating System ( Apple Computer; 800-909-6260; $699) is a slightly more compact unit without the built-in wireless capability. Both have proprietary graphical user interfaces (a Windows-like display that lets you use the system); E-mail, fax, and paging capabilities; databases that include address books and calendars; and the ability (supposedly) to read your handwritten notes. I say "supposedly" because the major shortcoming of PDAs in general and of these two specifically continues to be their spotty ability to read the handwriting of individual users.

The first-generation MessagePad was legendary for its notoriously poor handwriting-recognition engine. The good news is that things have improved dramatically. The bad news is that the newest MessagePad still has a very long way to go.

The basic idea is that you write on the screen with a blunt pen, called a stylus, and the MessagePad converts your scrawl into computer text. By continuously "learning" about your writing, the software tries to improve its accuracy. But that entails your going back and correcting mistakes each time so that it doesn't learn the wrong things. And that is a time-consuming, extremely frustrating, and sometimes fruitless process. For example, I failed to get the MessagePad to recognize the word if written in cursive, no matter how many times I wrote, linked, separated, or modified the two letters. Printing letters and numbers worked better, but overall I found the recognition process inadequate. With the Envoy, cursive writing wasn't an option at all, and even my printing gave me output so poor it was nearly useless.

The fastest way to input text in both products is to use a graphical keyboard that you summon up on screen; then you hunt and peck the characters you want with the stylus. (The MessagePad also has an optional external keyboard that works well but makes the PDA harder to carry around.)

Still, even if these machines are just barely adequate for composing messages, they're both excellent for receiving information. The hottest part of the Envoy is the feature that constantly checks for incoming items. That means that E-mail, pages, and faxes are automatically retrieved and put into your inbox--when they arrive. The automatic-retrieval feature is always on, when you're performing other functions or when the device is turned off. There's no need to dial in or check anything; when a message is waiting, a light on the outside of the unit blinks.

The less-expensive MessagePad doesn't have a built-in communicator, so you have to use its one PC-card slot to install a modem, which you can connect to either a cellular phone or a common phone jack. You also have to do the periodic dial-in drill to send or receive data.

Both of the units are compact, have legible screens--the MessagePad has soft backlighting--and provide solid contact-management and database features. The Envoy screen has an appealing 3-D graphic of a desktop; the MessagePad, drop-down menu items at the bottom of the screen.

A ton of second-party software is available for both units, and both claim to be able to interface with a wide range of computer data. Both connect to ordinary computer printers with minimal fuss.

The MessagePad is an economical choice if you don't need instant access to messages or if you already own a cellular phone­modem combination. But if you're starting from scratch and want on-the-fly communications, the Envoy is unquestionably better. It comes ready for wireless use, is extremely intuitive, and is very compact. E-mail me from the airport departure lounge, and tell me how you like it.

David Abrahamson is a major in the U.S. Army; he is stationed at the Pentagon.