Electronics have become a ubiquitous part of fitness and recreation. You use a GPS to navigate and track your speed, distance and vertical. You use a heart rate monitor to measure your calories burned and heart rate. You load your iPhone with all kinds of music and apps to power you through. Heck, you may even load your sneakers with electronics.
While electronics can enhance your experience, they can also be dangerous if you're spending time trying to get a readout rather than paying attention to the ground in front of you. What you need is to be able to glance at the display for a half a second, get the information and then put your eyes back on the road. Thing is, the compact nature of watches, GPS units and bike computers can make them difficult to read at a glance, especially if your vision isn't perfect.
Dual Eyewear sports sunglasses integrate bifocal-like lenses, putting a small magnification zone in the lower, inner corner. Look through it and get the magnifying power you need to see those numbers quickly and surely. The greater lens is just a regular polycarbonate sunglass lens. Several reviews that we've read indicate that magnification works effectively without hindering regular vision.
Dual Eyewear sunglasses come in three different magnification levels, +1.5, +2.0 and +2.5. The company suggests that those looking to use the sunglasses in the car, motorcycle or bike drop down a level from what they'd use when reading a book. Sunglasses are offered in several frame styles with brown or smoke lenses. Interchangeable lenses in amber and clear are also available for the SL2 model. The retail price of all models is US$49.95.
Source: Dual Eyewear via Gear Junkie
The advice on magnification is good, if you use say a +2.5 reading lens, then for a bicycle, car, motorcycle use you will only want a +1.5 or +2.0 ...