It's an increasingly IM-oriented world, in both home and business circles. Many people spend their entire day with at least one IM client running on their PC in order to stay in touch with friends, family, and colleagues. Usually, though, all of that human contact goes away when you leave your desk. Thankfully, along with Geodesic's Mundu software, your cell phone can help. Some handsets ship with rudimentary IM software built in, but smartphones don't usually come with that capability. Geodesic attempts to rectify that situation with Mundu IM V4, the company's latest mobile instant-messaging program. The Palm OS version of Mundu is stellar, but the Windows Mobile version needs plenty of work before I can recommend it.

Mundu is an IM aggregator, like the popular desktop software Trillian. It works with AOL, Google, ICQ, Jabber, MSN, and Yahoo! accounts. Aside from instant messaging, Mundu lets you send and receive files, and share photos taken with your phone's built-in camera. The program can group contacts and set up conference chats with three or more people, even when those people are all using different instant-messaging services. Mundu also lets you use boldface, italics, emoticons, and many of the other features you're used to with desktop IM clients.

Mundu is available for Palm OS and Windows Mobile Smartphone handhelds. Currently, there is no Windows Mobile for Pocket PC version, nor is there one for BlackBerry or Symbian handhelds yet, though Geodesic maintains that these are in the works. Unlike Agile Messenger, which costs $29.99 a year, you can own Mundu for a one-time fee of $11. That makes it a serious bargain: Keep your phone for two years and you'd be paying less than one-fifth of what Agile Messenger would cost.

Let's start with the good first. On my test Palm Treo 700p, Mundu looked fabulous, with all the icon and tabbed-interface conveniences you'd expect from a desktop IM client. Test chats worked back and forth without a hitch, even when other users were on non-native chat clients (such as Apple's iChat). I did run into one minor glitch, though: Bold text didn't show up on the other party's screen when that person was using Omnipod (a third-party chat client). But the program was very responsive, handling multiple chats from different IM accounts simultaneously with aplomb.

My experience with Mundu running under Windows Mobile was much less positive. No one is suggesting that the Motorola Q is a fast smartphone, but its 312-MHz CPU is quicker than the one in the Samsung BlackJack and the T-Mobile Dash. Yet the Windows Mobile version of Mundu took about 20 seconds to boot up, even on the Q, and, disturbingly, dropped back to the home screen twice during this process, only to return on its own and keep booting.

In yet another Windows Mobile problem, Mundu displayed a number of my contacts as off-line, even though I knew they were online. It turns out that Mundu can't see any AIM users that are logged in through other chat clients, such as Apple's iChat or Omnipod. That's an unworkable limitation: Lots of people log in with clients other than the native AIM version.

These weren't the only issues I encountered with Windows Mobile, either. On the Q, Mundu only used about half the width of the screen to display chat text, which was frustrating. It dedicated entire lines to the name of the person (such as "myAccountName:") and would only start the actual conversation text on the following line. Combine these two quirks and you have very little space to work with. In addition, Mundu gives the appearance of a tabbed interface, but you can't actually use the tabs for multiple chat windows on Windows Mobile like you can with the Palm OS version. Even when I had multiple windows open, I could only see one tab. What's the point of the tab, then? Geodesic claims that fixes for some of these graphical glitches should be available by the time you read this.

Keep in mind that all of this isn't a black mark against Windows Mobile in general. Though the Palm OS has a higher-resolution screen and generally feels faster than Windows Mobile, there are some fine apps that run flawlessly on Microsoft's mobile OS, including Google Maps for Mobile and SlingPlayer Mobile. Clearly Geodesic has more work to do with Mundu on the Windows Mobile side. On Palm OS, the razor-sharp graphics and multiple windows all lend a polish to the program that's largely absent from the Windows Mobile version.

Version differences aside, Mundu contains some other interesting features. It can send e-mail notifications whenever you receive new mail in your Gmail, MSN, or Yahoo! accounts. It supports some European languages, too, so you don't have to chat exclusively in English. It also has a background mode, which is no big deal under Windows Mobile but is significant on the single-tasking Palm OS. Finally, Mundu can save and archive your chat conversations the same way your desktop PC does (though you'll want to have enough free memory available for this purpose).

Going into this review, I was hoping that Mundu was as good as the more expensive Agile Messenger. On Palm OS, it most assuredly is, but Mundu IM V4 feels unfinished on Windows Mobile. Its puzzling interface oddities and inability to resolve idle AIM users put it seriously short of the mark. (If it weren't for the excellent Palm version, I would rate it around a 2 out of 5.) Palm OS users, meanwhile, can buy with full confidence, since Mundu is equally as good as Agile Messenger and much less expensive.