The computer micro-chip -- mainstay of Atari and digital alarm-clock calculating watches, spaceships (real and play), pocket stereo systems and burglar alarms -- now is emerging as a kind of combination baby-sitter, tranquilizer and panic button for the aged and infirm of independent persuasion.

Medical Emergency Alert's potential, in fact, for permitting independent living is perhaps its most significant characteristic.

One of several similiar systems in limited locations, Med-E-Lert is the first to attempt to set up a nationwide emergency network which, at the squeeze of a button, eventually will be able to dispatch emergency assistance to anyone almost anywhere in less than a minute.

Med-E-Lert was devised by an electronics engineer in Florida as an outgrowth of wireless electronic security systems he had been designing and manufacturing. As he looked at increasingly sophisticated security systems, more and more he saw the potential -- and the need -- for some sort of medical emergency reporting system.

In less than a year of operation, Med-E-Lert can boost several success stories among its nearly 2,000 users in 45 states and the District of Columbia. (So far only Alaska, Hawaii, North and South Dakota and Wyoming are without distributorships.):

An 84-year-old woman in Minnesota's sub-zero weather last winter slipped on the icy stoop outside her house and was unable to regain her footing. She remembered the remote device she had reluctantly agreed to carry in her pocket. Still skeptical, she squeezed the amulet. Within 10 minutes she had been carried inside, very little the worse for the frigid experience.

Retired Silver Spring attorney Howard Larcombe, 69. Paralyzed on his left side from a stroke, he fell and broke a hip two years ago. He lay for hours, he says, "between the sink and the toilet" before he was found. Now he wears a Med-E-Lert pendant and continues to live in his own house. "Not a chance," he says, "I could do it without it."

Linda Atkins, a Fairfax Hospital physical therapist who heard about Med-E-Lert from that hospital's social-work department. Her father-in-law had a stroke which left his communications skills impaired. "But," she says, "he was determined to go back to his own place. To my way of thinking in his apartment or thinking about a nursing home . . . and I don't think he'd have gone willingly. . . ."

It sounds like magic -- amulets, medallions, pendants, might as well say, magic lamps . . . but of course it's all as scientific as Star Raiders.

The pendant or medallion (either worn around the neck or carried in a pocket) contains a miniature radio which, when gently squeezed, sends an emergency signal to a control unit plugged into a telephone jack in the user's house. (It can be activated from at least 200 feet away and, depending on conditions, even from 300 feet or more.)

When activated, the control unit first gives off an audiable distress signal, then activates a digital communicator which captures a telephone line and sends a specially coded emergency signal to a 24-hour Emergency Monitoring Center.

The center's computer, within a minute, tells the (human) monitor where the signal is coming from and, according to pre-recorded information, what the problem is likely to be and which emergency authority and/or relatives or neighbors should be notified. While the human monitor is doing the notifying, the computer sends back a signal that turns off the distress noise, thereby notifying the user that help is on the way.

Emergency authorities or relatives can first phone the subscriber and, if there is no answer, proceed with emergency action.

Promoters of Med-E-Lert claim their system is more versatile and less susceptible to false alarms than other similar alerting systems now beginning to turn up in various parts of the country -- such as the hospital-based Lifeline program in Boston and New York.

It is not cheap -- about $1,200 to buy the unit plus $180 a year to operate the computer center. (That's about the same as a top-of-the-line TV recording tape-deck unit.) There are lease and lease-buy arrangements for Med-E-Lert and eventually, its manufacturers hope, it will be covered, at least in part, by Medicare, Medicaid and all health-insurance policies. Rep. Margaret Heckler (R-Mass.) has introduced a bill bringing all "personal emergency systems" under Medicare.

Fraternal, charitable and senior organizations who buy as groups receive significant discounts. Units then can be loaded or sublet to members who might not be able to afford them as individuals.

The peace of mind the device offers to subscribers who prefer to live alone and to their families is probably the system's biggest selling point, its distributors believe. They point to government figures which suggest that nearly a quarter of a million old people are in nursing homes who really do not need to be, who could live independently, perhaps with nothing more than this kind of electronic backup.

It is virtually limitless in the kinds of emergencies it can be used for -- from burglaries to fires to heart attacks to falls. Additional units may even be placed in the house of a neighbor or relative (usually within the same phone exchange) so that the first distress sound may bring almost instant help -- or at least comfort until skilled help arrives.