Perhaps the old slogan "a chicken in every pot" should be updated to read "a phone in every car."

First came the mobile radiophone, whose availability was limited when only a small number of frequencies were set aside for transmission of their signals. Next came a computer-based technology called cellular radio, with the potential for putting a mobile phone within reach of nearly everyone who wants and can afford one.At the same time, there's progress on the beeper front. Eventually, a nationwide paging system could result from cooperation between National Public Radio and Mobile Communications Corp. of America.

All this may be only the beginning. "Eventually," says Stuart Crump, the editor of Cellular Radio News, a monthly letter published in Washington, "I see the . . . hip phone, the wristwatch phone, the briefcase phone, . . . replacing the desk phone in all but densely populated areas. And maybe there, too."

The prospect could be more daunting than exhilarating. Being always "on call" is not everyone's idea of the good life. But technology will not be denied, and as the century draws to an end Dick Tracy's wrist-based communications system is looking less fanciful all the time.