In some ways, the mere existence of these devices is promising, because it demonstrates a level of standardization that benefits a range of consumer electronics. In the last year or so, a few key applications, operating systems and processors finally have achieved critical mass. Examples of this trend include MP3 audio, Windows CE and the ARM cores, respectively.

These emerging standards have two important effects. First, they draw developers, making it easier to find the bits and pieces needed for a convergence device. MP3 decoders, for example, are available for most popular embedded processors. Second, they create confidence in the interoperability and longevity of these products: It makes sense to build a camera into a cell phone only if users can share the pictures with their friends.

But as your mother told you, just because you can do something doesn't mean you should. Consider the refrigerator/PC combos touted in recent years. While it is possible-even practical-to add high-tech features to a refrigerator, it is hard to imagine buyers for such devices. Refrigerators last for decades, while consumer electronics are often obsolete in a matter of years. Who wants to use the same PC for 20 years? And the potential for unintended consequences in a convergence device can be frightening. What if the PDA half of your souped-up cell phone crashes and prevents you from placing an emergency call?

Clearly, the technology needed for powerful convergence devices is within reach. The challenge for today's product designers is to find combinations that add utility, not just technical dazzle, and to think carefully about the awkward, and potentially hazardous, effects of these combinations.

Jeff Bier is the General Manager of Berkeley Design Technology Inc. (www.bdti.com), the DSP Technology Analysis and Software Development Company. Kenton Williston of BDTI contributed to this column.