From fighter jets to Google Glass: Head-up displays make the jump to mainstream gadgets Technology that was for decades the preserve of real-life Mavericks and Gooses (Geese?) is making Top Guns of us all - and nobody's being shot out of the sky. The head-up display, known in air-force circles by its acronym, HUD, has launched from the military to the consumer realm with a range of magically projecting devices laying data over the view ahead, be it from the driver's seat, through a skier's goggles or the weird glasses worn by that guy on the train. But, first up - what is this thing? A head-up display is, in simple terms, a transparent display that tells you about what you're looking at without requiring you to stop looking at it. In a fighter jet, that might be your altitude or the position of enemy planes, when a split second spent looking down at your instruments could be the difference between life and Tom Cruise's tears (Top Gun references end here). In a car equipped with Garmin's new HUD sat-nav, reviewed here last week, it might be your speed and arrow telling you when to take the third exit at the roundabout. The device, just released in the UK, is roughly the size of a standard satnav but sticks to your dashboard and projects information upwards on to a bit of transparent film stuck to your windscreen. The data is sent to the device wirelessly, via Bluetooth, from your phone, which must be equipped with a compatible navigation app. Garmin's device isn't revolutionary but represents the arrival of military hardware that became an expensive consumer option into the affordable mainstream (the unit and app together cost less than £200). By some measure, it has taken 110 years for the technology to become small and cheap enough to make that journey to market. The military aviation HUD can be traced to a patent filed in 1900 for the reflector sight. That crude device, later deployed by fighting forces everywhere, superimposed a light-beam target symbol over the view through a gun's sights. Displays evolved to include further information such as airspeed in planes before becoming highly sophisticated and present also in civilian aircraft. The car industry, perhaps inspired by the intelligent Knight Rider car of David Hasselhoff fame, began incorporating HUDs into dashboards in the late 1980s - if only as a niche, luxury option, often requiring the installation of whole, HUD-ready windscreens. Now, car and tech companies are racing to offer the best HUD capability, marketing their more affordable devices as safe at a time when drivers have never been more distracted. Google Glass will hit the shelves early next year (Getty Images) Last month, at the Frankfurt Motor Show, a Garmin rival emerged in the shape of Pioneer's NavGate device. More head-up than any other, it attaches to the driver's sun visor, projecting information on to the windscreen way up at eye level. An experiment commissioned by Nissan and carried out at the University of Michigan found that braking reaction times were better among drivers presented with information at a higher level. The closer the information to the focus on the road ahead, the theory goes, the safer you are (reaction times were notably best, however, when drivers were presented with no potential distractions). Among built-in HUDs in cars, Ford and BMW offer some of the smartest. Suitably specced Lexus cars, meanwhile, will project large, red brake warnings on to the windscreen. Away from cars, the biggest frontline in HUD development is right in front of our eyes. Google's Glass devices ought to need no introduction after the huge attention they have received since early adopters began wearing them earlier this year. In military terms, Google Glass is an optical head-mounted display (OHMD) of the sort that first appeared fixed to the helmets of soldiers. But the principle is the same as in the HUD - the projection of information right into your field of view. In the fledgling market for wearable technology, which also includes smart watches, rivals also circle. Intel, the computer chip giant, last week invested big money (about £2.5m) in Recon Instruments, a Canadian company that has made prototype displays for sporty consumers. Its Jet device, due for launch next year, is built into a pair of sunglasses for cyclists and shows the rider his speed, heart rate or power output, among other bits of information. With a touch of a button, it takes a photo of what you're seeing. Recon snow and cycling goggles A similar device made by Recon slips into a pair of ski goggles to bring data to snow riders such as vertical descent, the time you just spent airborne, or the location of your friends if, say, you're skiing in the trees and have become separated. Previously, sporty prototypes have been made or proposed by other companies for smart swimming goggles that display the number of lengths you've done. In Japan, meanwhile, an entrepreneur called Takahito Iguchi claims to be preparing to launch his Telepathy One device, a closer rival to Google Glass than Recon that would allow you to stream your point of view to anyone interested enough to watch it. But as our eyes are increasingly assaulted by optically challenging new technologies, from HUD devices to 3D televisions, one scientist is looking anew at the causes of motion sickness or its digital counterpart, simulation sickness. Again, it's a phenomenon with military roots. US army chiefs struggled years ago to stop soldiers getting queasy while undergoing simulated training. Now reports flood the internet of sickness among tech users caused by effects as seemingly innocuous as the moving background in Apple's new iPhone software. You've been warned. Internet Creator of the internet is a hotly contested title but what's certain is the key role played by the US Army's Advanced Research Projects Agent (now DARPA), whose Arpanet linked computer networks from the late 1960s and laid the foundations for the modern net. Satellites orbiting the earth that now allow you to plot a route to the nearest pub were first sent to space by the US Navy in the 1960s. GPS was to remain a military technology but when Russian jets shot down an off-course Korean Airlines flight in 1983, killing 269, President Reagan proposed GPS be made available for civilian use to prevent a repetition. Drones Deadly drones such as the controversial Predator, used widely in Afghanistan and Pakistan, have been around for more than 15 years, but unmanned flying craft that can be controlled via tablet or smartphone are now booming in the consumer world. Many include video cameras that can transmit live footage back to ground level. They stretch the definition of technology but constitute perhaps the military's greatest and most peaceful contribution to civilian life. M&M's were conceived when Forrest Mars, son of Mars founder, Frank, observed soldiers eating chocolate pellets in hard candy shells that prevented melting in the heat of the Spanish Civil War. By WWII, Mars' version was so popular that they were included in US Army ration packs. Zoah Hedges-Stocks