What's Your Favorite Piece of Fitness Technology?

Often times, we only think of the technology that makes our lives more productive or entertaining. But what about the stuff that allows us to have the most fun outdoors?

So, what's your favorite piece of technology designed for sports, exercise or general fitness. It could be technical clothing, bullet-proof headphones, a GPS device or even a bicycle. What's changed your workouts or adventures the most?

Image by Annette Shaff / Shuttersotck