Back when 3Com debuted the first Palm Pilot, there wasn't a lot you could do with it by today's standards -- track your diary and phone numbers, and perhaps download some games or software through your computer. These days however, personal digital assistants (PDAs) are beginning to merge with other devices, notably mobile phones, to create a whole new category of gadgets. Industry data provider IDC calls them SHDs -- smart handheld devices -- and they include everything from mobile phones to minicomputers. And yesterday's PDA is right in the middle of them. Many products on display at CeBIT this year can help you turn your handheld into a mobile phone, a web browser, a global positioning system or a security device.

Most of these add-ons to the existing handhelds come in the form of expansion modules which plug into a data port, or 'sleds' which attach to the bottom of the devices. REALVision's GSM phone, for example, slides onto the bottom of a Palm V PDA. Kodak has also introduced a digital camera sled for the newest Palm m500 and m505 at CeBIT this week. Handspring, whose Visor products run a licensed version of the Palm operating system, has its own plug-in format called Springboard, which can take modules like MP3 players, GPS receivers and Handspring's own GSM phone.

Competition is increasing in the market for handheld operating systems -- Palm, Microsoft and Symbian are the major players -- and the proliferation of standards for handheld plug-ins muddy the waters further. Sony, a Palm OS licensee, uses its own Memory Stick technology for its family of computers and personal electronics, and will release Memory Stick expansion modules starting next year with a fingerprint scanner, GPS receiver and digital camera. Meanwhile the newest Palm handhelds take an SD card -- a standard developed by Panasonic, Toshiba and over 200 other companies. Compaq's iPAQ, which runs on the Microsoft Pocket PC platform, comes with a media slot, and a sled adapter which fits the larger Compact Flash card. Handspring, meanwhile, licenses its Springboard plug-in technology to other equipment makers as well.

All of these companies offer compelling reasons for wanting their own standards: although it looked at all the possible options, Palm representatives told journalists at CeBIT, it declined to go with Sony or Handspring's expansion options primarily for 'form factor' reasons - basically, the overall look and feel of the product, or, more succinctly, its coolness factor. Handspring cites the same reasons for wanting to develop its own standard -- easy plug-and-play, and room to grow the module itself. Sony, meanwhile, built the Memory Stick to facilitate interoperability among its own products.

Why not make it simple and integrate these features into one device? Cost is the main reason: prices for PDAs across the board are getting more competitive, and extra functionality can push the price of a given handheld out of the band of acceptability. But 'form factor', is a large part of it as well. As the success of 1999's Palm V proved, consumers buy PDAs as much for their looks as for their functionality; because of this, manufacturers have been reluctant to sacrifice their products' slim profiles for added features which may or may not find a market.

But as the demand for networked devices increases and as miniaturization and mass production bring size and price down, added functions and communication abilities will be integrated into the devices itself. One of the first of these hybrid devices to hit the market will be Siemens' SX45 handheld, in stores this fall. The device runs on the Microsoft Pocket PC platform, and will allow connections to a GPRS network, the always-on mobile Internet access which is touted to replace WAP this year. Although it doesn't need a sled or an add-on pack, the device is still slightly larger than most handhelds on the market and will carry a heftier price tag in the range of about ¤1,000. "The long-term goal is for these devices to be integrated, single units." says Chris Cadwell, a marketing director at Handspring. "I think most of the industry is working towards that day. Once it gets cost-effective enough, it'll be a very compelling product."