If you regularly swim laps in a pool, chances are that you wear goggles so you can follow the lane markers on the bottom. For triathletes swimming in lakes or the sea, however, there are no lane markers. Instead, they have to periodically look up towards marker buoys, and may even then proceed forward in a time- and energy-wasting zig-zaggy pattern. That's why OnCourse Goggles were created. Using LEDs, they show the wearer how to stay … well, on course.
The goggles contain an electronic compass, accelerometer with tilt compensation, USB-rechargeable lithium-polymer battery, and a microprocessor running custom software. They also have two colored LEDs, one in each eye cup.
To use them, you start by looking towards your destination (probably a buoy or landmark), then pressing a button on the goggles to save that heading. Once you start swimming, the onboard electronics will detect any deviations from your course toward that point – this includes drifting due to currents or wind.
In order to alert you to the situation, the LED on the side that you're mistakenly wandering toward will first turn amber. If you continue in that direction, it will turn red. Once you've corrected your course and are heading straight again, though, both LEDs will turn green. As long as you continue to keep them both green, you know that you're on course.
Assuming that the buoy you're swimming for is just a waypoint (and not your final destination), you briefly stick your head out of the water upon reaching it, set a new heading on the next buoy, then continue on your way.
The goggles also feature a soft silicone gasket, polarized lenses, an anti-fog coating, and UV protection. Charging the battery takes 45 minutes, although there's no word on how long that charge will last.
If you're interested in getting a pair, OnCourse Goggles are currently the subject of a Kickstarter campaign. A pledge of US$149 will get you a pair, when and if they reach production. The planned retail price is $199.
You can see a simulation of how they work, in the video below.