AfterShokz is one of a handful of companies making bone-conduction headphones, having launched its brand in early 2012. Unlike conventional headphones and earbuds that use the eardrums to transmit sound, AfterShokz headphones rest in front of your ear and use bone-conduction technology to transmit sound through your cheekbones to your inner ear, bypassing your eardrum completely. The technology, originally developed for military personnel, has been around for a while, but AfterShokz and others have turned it into a niche consumer product.
Although the headphones work just fine, serious music listeners won't be impressed by the sound quality. After all, these are the antithesis of sound-isolating headphones designed to block out ambient noise. With these, your ears remain completely uncovered and you can easily have a conversation with someone while listening to music. AfterShokz has been targeting joggers, bike riders, skiers, skateboarders, hikers, and others who want to stay "connected to their surroundings" (on Amazon, I saw a pair of waterproof bone-conduction headphones for swimmers).
I've been playing around with a second-generation model, the AfterShokz Sportz M2 ($69.95), which has a built-in microphone for making calls. I hadn't tested the original AfterShokz model, so I didn't have reference point, but company reps informed me that 21 improvements were made to the headphones, including an upgrade in sound quality. Some of the key differences are that the inline battery box is smaller and lighter and includes volume controls, as well it should. The battery is rechargeable via a Micro-USB connector.
The earphones are "sweat-proof" and water-resistant but not waterproof. They come come with a nice though somewhat bulky carrying case.