What gadgets will you want on your car three, five or 10 years from now? You’ll find the answers on some of the new luxury cars in showrooms today.

As a general rule, the most valuable automotive technology tends to follow a trickle-down route. It debuts on elite, upscale cars, proves its usefulness and eventually finds its way to more popular, more affordable cars.

Take anti-lock brakes, for example. Fifteen years ago, you found them only on BMWs, Cadillacs, Benzes and the like. As consumers recognized their added value, however, automakers began offering them on more and more vehicles.

The same goes for other practical technological innovations. In a few safety-related cases, of course, the federal government intervenes, and the trickle becomes a sudden flood. For instance, tire pressure monitors—once found exclusively on a few expensive sports cars with run-flat tires—are now required on all ’03 models.

What are today’s best candidates for trickle-down popularity? These recent innovations look like good bets:

• Brake by Wire. If you’ve flown in a big commercial airliner anytime in the past 20 years or so, chances are it used “fly-by-wire” technology. Instead of a hydraulic system, wires or fiber-optic cables carried the pilot’s commands electronically to motors, which operated the flaps, slats and other control surfaces.

Now, this sophisticated aircraft technology has trickled down to cars. The ’03 Mercedes-Benz SL sports car employs a system called Sensotronic Brake Control—essentially, brake by wire.

In Mercedes’ system, stepping on the pedal sends an electronic impulse to sensors and a computer, which processes that input along with signals from other sensors in milliseconds. Through an electric pump and a high-pressure hydraulic system, the computer metes out force to brake each wheel separately, as needed.

The result? Much shorter, surer stops, especially in emergencies, when the computer recognizes the driver’s quick movement from the accelerator to the brake pedal. And the system can even brake the vehicle automatically when you lift your foot from the accelerator in a traffic jam, or stop it extra softly and smoothly in around-town driving.

Although Mercedes’ Sensotronic system represents the first application of drive-by-wire technology to brakes, other carmakers—most notably, Saturn—are using electronic steering on certain models. Expect electronics or electrohydraulics to replace more and more mechanical or hydraulic systems in the future.

• Idle-Off Engines. The engineers who cooked up the hybrid powerplant know all about squeezing the maximum mpg out of an engine. For example, the Toyota Prius—powered by an electric motor-gasoline engine combo—automatically shuts down the gasoline engine when the car is sitting at a stop light or otherwise going nowhere.

Leave it to Mercedes to apply the idle-off idea to all-gasoline engines. In early ’03 models of the12-cylinder S600 and CL600, six of the cylinders power down when they’re not needed. Mercedes says the technique saves up to 2 mpg.

Curiously, Mercedes is introducing newer versions of its 12-cylinder engine that don’t have cylinder cut-off. But the idea seems too good to go away. GM reportedly has a similar system, called Displacement on Demand, ready for some of its V-8 trucks next year.

• Crash Anticipation. The concept of a vehicle readying occupants for a crash began years ago with automatic safety belt pre-tensioners, now standard equipment on many models in all price ranges. They instantly spool up slack in the belts for a snug fit.

Pre-crash prep reaches a whole new level of sophistication in the Pre-Safe system on the new Mercedes S-Class models. Using inputs from sensors in the stability control and anti-lock braking systems, Pre-Safe detects a severe skid or other behavior that might signal an imminent crash. Then, it not only activates the safety belt pre-tensioners, but also adjusts the angle and fore-and-aft location of the seats to optimize the occupant’s position in a crash and automatically closes the sunroof. If no crash occurs, the belts, seats and sunroof return to their original settings.

• See-in-the-Dark Screens. Since 2000, some Cadillac and Buick models have offered Night Vision, an infrared-sensing system that lets drivers see otherwise-invisible people, animals and other objects that reflect or radiate heat in the dark.

This year, Lexus debuts the first “active” Night View cameras on its LX 470 sport-utility vehicle. Unlike passive systems, which detect infrared waves from obstacles themselves, Lexus’ Night View projects near-infrared beams from two lamps in the grille. A special camera picks up the reflections and projects images low on the windshield, much like a head-up display. Lexus claims it generates more detailed, higher quality images of everything on the road up to 500 feet away—about three or four times the distance illuminated by low-beam headlights.

DaimlerChrysler has tested a similar infrared projection system and hopes to make it available soon.

• Voice Activation. Vehicles that respond to voice commands have been making people ooh and aah at car shows for years. In 2001, BMW’s iDrive system began making drivers speak to their cars when they wanted to adjust the climate controls or change the radio station. Unfortunately, iDrive’s complexity also made some owners swear a blue streak when they couldn’t figure out how to program the thing.

Now, Honda owners will be talking to their cars, too. In a perfect example of trickle-down technology in practice, the ’03 Accord has become the first vehicle under $30,000 on the U.S. market to offer an optional voice-controlled satellite navigation system.

• Track Lighting. Here’s an on-the-road innovation that you can’t buy at any price—at least, not yet. This year, GM intends to equip some of its European Opels with headlights that swivel up to 15 degrees right or left, depending on the steering angle and speed of the car, to track curves in the road ahead. Other lights turn 90 degrees to shine around corners at intersections. Europe has to change its safety regulations to make these so-called “adaptive” lights street-legal. Similar changes would be needed in standards here, so don’t expect swiveling headlights just around the corner.