First, drivers looked to their dashboards for directions from GPS navigation systems. Then, the tech companies started making portable GPS units. Now, just about everyone carries a smartphone, which can easily double as a GPS device with a simple map app. With so many innovations, how could GPS navigation systems get any easier to use?

Enter the heads-up display. Also referred to as HUDs, heads-up displays were originally used in fighter jets for tracking targets and monitoring vitals. Now, these HUDs are becoming more common in cars. And why not? A heads-up display works by projecting important data to a small section of the windshield, allowing drivers to view this data without taking their eyes off the road.

Data projected from HUDs can be simple or complex. A portable HUD may simply project GPS directional data, while an in-dash factory HUD may be synced with features such as adaptive cruise control, highlighting which vehicle your car is gauging for adjusting its speed. The best part about these HUDs is they don't need to be expensive. For just a few bucks, you can download a free smartphone HUD app and then upgrade it with 3D route travel.

DigiHUD, GPS HUD, Navier HUD and HUDWAY are examples of such apps. The HUDWAY app includes 3D route directions for free, but the HUD is much more simplistic compared with an app like Navier HUD, which requires a paid upgrade to receive real-time route instructions. Also, keep in mind these phone apps aren't always as good as the real thing. People with larger smartphones with more vibrant screens (i.e. the Samsung Galaxy lineup) may be impressed, but cheaper phones with smaller screens and dimmer displays may not even see the HUD appear on their windshields.

For better performance, consider upgrading to an aftermarket HUD system. Retailing for around $100, the Garmin HUD is a smartphone-sized device that sits on your dashboard to provide map instructions, distances to upcoming turns, vehicle speeds, the speed limits of the roads you're traveling and more. The Garmin also offers voiced instructions to help drivers stay focused on the road. A big advantage of this aftermarket HUD device is the option to either project data onto the windshield (using a small patch of reflective film that sticks to the windshield) or to a small plastic screen that flips up from the device itself. This ensures the device's effectiveness.

Keep in mind, Garmin isn't the only company offering aftermarket automotive HUD solutions. That said, nothing beats the HUDs being included in some of the most high-tech cars on the market. The 2013 Cadillac ATS turned heads with a full-color HUD that hovers just beyond the steering wheel. Remarkably, the HUD projection is visible at all times, even in direct sunlight. Other automakers that have already included HUDs with their new cars include BMW, Toyota, Ford and GM - and the list goes on.

As more vehicles gravitate toward safety, HUD technology is only going to become more widespread in entry-level vehicles. Next time you get behind the wheel, imagine being fed real-time directions by an "on screen" interface that doesn't require looking away from the road. We may not be in the era of flying cars, but that doesn't mean you can't feel like a fighter pilot when taking your next road trip.