Imagine this: you walk up to the forbidding steel door in your ultra high-tech office complex. There’s no handle, no lock, no slot for a card, no eyeball reader, no keypad, no place for a palm print.

Are you stuck outside?

No way. You simply twitch your left arm forward, flex your muscles and a hidden sensor reads the security chip implanted under the skin on your bicep and the door slides open.

Some may think this is wonderful; others are probably appalled. But the technology exists and is already in operation in some places. All it takes is an implant the size of a grain of rice. (Or, if the idea seems too Orwellian, about the size of your average mouse dropping.)

And the applications are endless.

Let us suppose that on a sunny afternoon you and your spouse want to have a cozy little nap and your screaming toddler wants to play outside in the yard. No problem. The kid has a security chip in her arm; if she starts to wander off the property, the chip — programmed with boundaries — realizes she is straying and zaps her with a minor electrical charge. And after she is zapped a couple of times, she picks herself up and toddles back to the house. Kind of like an invisible fence for dogs, only easier to operate.

Or take the implications for dieting. You must have noticed that every day there’s a story or two about how aging baby boomers are growing fat and unhealthy. Too much food, too little exercise. Enter the tiny chip, programmed in the aversion mode. You reach for that plate of french fries or that piece of chocolate cake and your little smart chip freezes your arm in mid-grab. So, you turn to your computer and there’s a message: one two-mile jog in 12 minutes or less equals one piece of cake. And if you want fries, shovel the snow from the driveway.

Simple and effective.

And, of course, the medical implications might be the most important of all. Your entire medical history can be encoded and slid under your skin, so if you are wheeled into the emergency room at 3 a.m., unconscious, the attending doctors can haul out a bar-code reader and see what you are all about.

“Hey, look at this,” says the first doctor. “This guy has had both peritonitis and mononucleosis. That’s a combination we don’t see much any more. Even polio. Wow, he must go back a long way.”

“Yeah,” says the second doctor, “but what about right now? I’m guessing he has a broken leg — unless he always has a chunk of bone sticking through his pant leg.”

“Nothing about that on his microchip,” says the first doc, “so we better go ahead and fix it. But look at the rest of his record: whooping cough, measles, shingles, high blood pressure, high cholesterol and his prostate looks like a chopping block.”

And surely the chip can reach beyond medicine.

Let us suppose that your nubile teenage daughter has taken up with bad companions. Specifically, a lout with greasy hair and baggy pants. Under the guise of a flu shot, your family doctor slides a little aversion chip into her arm. The next thing you know, she has hooked up with a guy in a tweed jacket and grey flannels whose idea of a hot time is watching Mister Roberts on DVD. And he is keen on Bible study, but only the New Testament.

I tell you, the uses of modern technology are endless. I’m thinking of experimenting by getting one implanted in one of my dogs. The only problem is, if she gets loose, she’ll probably start walking into high-security buildings and raise hell. IE